JP2014031963A - Light reflection unit and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light reflection unit that reduces distortion of a reflection plate and decrease of reflectance of the reflection plate.SOLUTION: The light reflection unit comprises a frame body 3 having a curved supporting member 7 that is curved in a concave arc shape. A magnet sheet 15 is provided on the concave arc surface of the curved supporting member 7. At least a portion of a reflection plate 4 made of a magnetic material is attracted by a magnetic force of the magnet sheet 15 and fixed to the curved supporting member 7. When the reflection plate 4 is fixed to the curved supporting member 7 in this manner, the reflection plate 4 is curved in a concave arc shape along the curved supporting member 7, and a reflection concave arc surface 16 of the reflection plate 4 is opposed to a heat collecting pipe 2 so that reflected light from the reflection plate 4 is collected onto the heat collecting pipe 2. Then, the reflection plate 4 reflects light onto the heat collecting pipe 2 in which fluid can flow, and the fluid in the heat collecting pipe 2 is heated.

Description

  The present invention relates to a light reflecting unit that reflects light to a heat collecting tube through which a fluid can flow, and a manufacturing method thereof.

  Conventionally, a coated product of a glass substrate has been used as a reflection plate in a light reflection unit for heating fluid in a heat collecting tube by reflecting light such as sunlight and infrared rays.

  However, in order to form a reflecting plate having a concave arc surface curved in a concave arc shape with a coating material of a glass base material, the manufacturing cost becomes high, and the glass base material is easily damaged by flying objects. Therefore, in recent years, a metal substrate is used as the reflector.

  As such a metal base material, an aluminum alloy or a titanium alloy mirror polished plate has been used in order to prevent the reflectivity from being lowered due to fogging due to rain or the like.

  In addition, these mirror-polished plates are excellent in workability, so that a curved surface processed into a concave arc shape was used as a reflector so that energy such as sunlight was concentrated and reflected easily. .

  Here, the mirror-polished plate that has been subjected to curved surface processing is generally subjected to curved surface processing after mirror surface processing because a special device is required for mirror surface polishing after curved surface processing, resulting in an increase in manufacturing cost.

  However, if the curved surface is processed after the mirror surface processing, irregularities due to processing distortion occur on the reflecting surface, and thus the reflectance is lowered.

  Therefore, a thin plate having a thickness of 0.5 mm or less is used as the reflection plate, and the reflection plate that is curved in a concave arc shape within elastic deformation so as not to be distorted is screwed and fixed to the frame body with a screw. (For example, refer nonpatent literature 1).

[online], Power Technology, Inc. [searched July 5, 2012], Internet <URL: http://www.power-technology.com/projects/holanikuatkeaholepoi/holanikuatkeaholepoi2.html>

  However, in the configuration of Non-Patent Document 1 described above, since a thin plate of 0.5 mm or less is used, the reflection plate is plastically deformed and distorted by screwing with a screw when attaching the reflection plate to the frame. There is a possibility that the reflectance of the reflecting plate is lowered.

  This invention is made in view of such a point, and it aims at providing the manufacturing method of the light reflection unit which hardly produces a distortion in a reflecting plate, and the reflectance of a reflecting plate does not fall easily, and a light reflecting unit.

  The light reflecting unit according to claim 1 is a light reflecting unit for reflecting light to a heat collecting tube in which a fluid can flow inside, a frame body having a curved support member curved in a concave arc shape, and a curved support member And a reflector made of a magnetic material. The reflector is attracted by the magnetic force of the magnetic attraction part, thereby forming a concave arc along the curved support member. It is attached to the frame body in a curved state and reflects light to the heat collecting tube.

  The light reflecting unit described in claim 2 is the light reflecting unit according to claim 1, wherein the reflecting plate is made of stainless steel having a thickness of 0.5 mm or less and containing 11% or more of Cr by mass% and having soft magnetic properties. This stainless steel is high-gloss rolled or mirror-polished and has a surface roughness Ra of 0.2 μm or less.

  The light reflecting unit according to claim 3 is the light reflecting unit according to claim 2, wherein the stainless steel is in mass%, C: 0.08% or less, Si: 3.0% or less, Mn: 3. It contains 0% or less, Cr: 11.0% or more and 30.0% or less, Ni: 10.0% or less, and N: 0.50% or less, with the balance being Fe and inevitable impurities.

  The light reflecting unit described in claim 4 is the light reflecting unit according to claim 3, wherein the stainless steel is in mass%, Al: 7.0% or less, Nb: 0.8% or less, Ti: 0.00. In addition to containing 8% or less, it contains at least one of Mo, Cu, and W so that the total content is 4.0% or less.

  The light reflecting unit according to claim 5 is the light reflecting unit according to claim 4, wherein the stainless steel is brightly annealed at a temperature of 700 ° C. or higher after high gloss rolling or mirror polishing, and has a wavelength region of 600 nm to 1000 nm. The light reflectance is 60% or more.

  The method of manufacturing a light reflecting unit according to claim 6 is a method of manufacturing a light reflecting unit that reflects light to a heat collecting tube through which a fluid can flow, and is a curved support member curved in a concave arc shape in a frame. A magnetic adsorption part having a magnetic force is provided on the surface, and a reflector formed of a magnetic material is adsorbed by the magnetic force of the magnetic adsorption part, so that it bends in a concave arc along the curved support member and reflects light to the heat collecting tube. The reflector is attached to the frame.

  The light reflecting unit manufacturing method according to claim 7 is the light reflecting unit manufacturing method according to claim 6, wherein the reflecting plate is made of stainless steel having soft magnetic properties, and the surface roughness of the stainless steel is low. Stainless steel is subjected to high gloss rolling or mirror polishing so that Ra is 0.2 μm or less.

  The light reflecting unit manufacturing method according to claim 8 is the light reflecting unit manufacturing method according to claim 7, wherein the stainless steel has a light reflectance of 60% or more in a wavelength region of 600 nm to 1000 nm. As described above, bright annealing is performed at a temperature of 700 ° C. or higher after high gloss rolling or mirror polishing.

  According to the present invention, since the reflecting plate is fixed to the curved support member by the magnetic force of the magnetic attracting part and attached to the frame body, the reflecting plate is hardly distorted, and the reflectance of the reflecting plate is hardly lowered.

  Moreover, since the reflecting plate is fixed to the curved support member by the magnetic force of the magnetic adsorption portion, the reflecting plate can be easily attached and detached.

It is a perspective view which shows the light reflection unit which concerns on one embodiment of this invention. It is sectional drawing which shows a light reflection unit same as the above.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 and FIG.

  In FIG. 1, 1 is a light reflecting unit, and this light reflecting unit 1 reflects light such as sunlight and ultraviolet rays to a tubular heat collecting tube 2 in which a fluid such as oil or water can flow. It is.

  For example, in a concentrating solar power plant, a plurality of light reflecting units 1 are installed along the heat collecting tubes 2, and the light reflected by each light reflecting unit 1 is collected on the heat collecting tubes 2. The fluid in the heat collecting pipe 2 is heated and converted into heat energy.

  The light reflecting unit 1 includes a frame 3, and a reflective plate 4 that reflects light to the heat collecting tube 2 is attached to the frame 3 so that reflected light from the reflective plate 4 is condensed. The arranged heat collecting tube 2 is supported.

  The frame 3 includes a pair of prismatic rod-like support members 6 that are arranged substantially in parallel with the heat collection tube 2 and are spaced symmetrically with respect to the heat collection tube 2 in plan view.

  In addition, one end in the longitudinal direction of one rod-shaped support member 6 extends from one end in the longitudinal direction of one rod-shaped support member 6 so as to bulge downward from one end of each rod-shaped support member 6 in the longitudinal direction. A curved support member 7 curved in a concave arc shape is integrally connected to the portion. In addition, the curved support member 7 is similarly connected to the other end part of each rod-shaped support member 6 in the longitudinal direction.

  Further, a plate-like support plate member 8 is attached to both ends of each rod-like support member 6 by being screwed with bolts 11 so as to intersect with, for example, orthogonally cross these rod-like support members 6.

  An engagement hole (not shown) is provided at the center in the longitudinal direction of the support plate member 8, and the support bar member 12 inserted through the engagement hole is connected to the support plate member 8 by the nut 13. It is fixed.

  Further, a tubular support tube member 14 opened in the horizontal direction is provided at the tip of the support bar member 12. The support tube member 14 has an inner diameter that is slightly larger than the outer diameter of the heat collection tube 2, and the heat collection tube 2 can be combined therein. As shown in FIG. 2, the heat collecting tube 2 is fitted into the support tube member 14, whereby the arrangement of the heat collecting tube 2 with respect to the reflecting plate 4 is maintained.

  The curved support member 7 is provided with a magnet sheet 15 as a magnetic attracting part having a magnetic force on a concave arc surface (not shown) which is an inner surface.

  The magnet sheet 15 is capable of attracting a magnetic material by magnetic force. The magnet sheet 15 is disposed by being attracted to the concave arc surface of the curved support member 7 by a magnetic force when the curved support member 7 is a magnetic material, and an adhesive when the curved support member 7 is not a magnetic material. For example, it is adhered to the concave arc surface of the curved support member 7.

  Here, the rectangular reflection plate 4 is made of a magnetic material, and both end portions in the longitudinal direction are arranged on the concave arc surface of the curved support member 7 via the magnet sheet 15 as shown in FIG. It is supported. That is, both ends in the longitudinal direction of the reflecting plate 4 are adsorbed by the magnetic force of the magnet sheet 15 and fixed to the curved support member 7 while being curved in a concave arc shape along the concave arc surface of the curved support member 7. Yes.

  Thus, the reflecting plate 4 fixed in a state where both ends in the longitudinal direction are curved is curved in a concave arc along the curved support member 7 over the entire longitudinal direction. Further, both end portions of the reflecting plate 4 in the width direction are supported in a state of being in contact with the side surfaces of the rod-like support member 6. Further, the corners of the end portions in the width direction of the reflection plate 4 are supported so as to be locked to the support plate member 8.

  Then, the reflecting plate 4 attached to the frame 3 in a state of being curved in a concave arc shape as a whole has a reflective concave arc surface 16 which is an inner surface on the heat collecting tube 2 so that the reflected light is condensed on the heat collecting tube 2. Opposite.

  In order to efficiently collect the reflected light from the reflecting plate 4 on the heat collecting tube 2, it is important to attach the reflecting plate 4 to the frame 3 so that the reflection forward concave arc surface 16 is not distorted.

Therefore, as the reflector 4, a stainless steel having soft magnetic properties containing 11.0% by mass or more of Cr, such as ferritic stainless steel, martensitic stainless steel, and metastable austenitic stainless steel, should be used. Is preferred. As the soft magnetic characteristics of the stainless steel, and more preferably the magnetic flux density _{B 10} is a 0.3MT (mT) or higher.

  Further, if the reflecting plate 4 is plastically deformed when the reflecting plate 4 is attached to the frame 3, the reflecting concave arc surface 16 is distorted. Therefore, the stainless steel forming the reflecting plate 4 has a thickness of 0.5 mm or less. It is preferable to be attached to the frame 3 by curving in the elastic deformation region.

  Thus, when the reflecting plate 4 is formed of stainless steel, it is necessary to maintain corrosion resistance against wind and rain, and the reflectance of light in the wavelength region of 600 nm to 1000 nm on the reflective concave arc surface 16 is important. . Specifically, in consideration of reflecting light such as sunlight and infrared rays, the reflective concave arc surface 16 preferably has a reflectance of 60% or more with respect to light in a wavelength region of 600 nm or more and 1000 nm or less.

  In order to ensure such reflectivity, high gloss rolling or mirror polishing is applied to the stainless steel so that the surface roughness of the reflecting concave arc surface 16 is Ra (arithmetic mean roughness) 0.2 μm or less. It is preferable to apply.

Furthermore, for example, when using stainless steel containing Al (aluminum) or Ti (titanium), by performing bright annealing at a temperature of 700 ° C. or higher after high gloss rolling or mirror polishing, the surface of the stainless steel is made of Al. An oxide film such as ₂ O ₃ or TiO ₂ is formed, which is preferable because the reflectance can be improved.

  Here, when stainless steel is used as the reflector 4, 0.08 mass% or less C (carbon), 3.0 mass% or less Si (silicon), 3.0 mass% or less Mn (manganese) 110. It contains Cr (chromium) in an amount of 3% by mass or more and 30.0% by mass or less, Ni (nickel) in an amount of 10.0% by mass or less, and N (nitrogen) in an amount of 0.50% or less with the balance being Fe (iron). And stainless steel composed of unavoidable impurities is preferred.

  C improves the strength, but if it exceeds 0.08% by mass, Cr carbide may be generated and the corrosion resistance may decrease. Therefore, the C content is preferably 0.08% by mass or less.

  Si improves the strength as the content increases, but if it exceeds 3.0% by mass, it may harden the matrix and deteriorate toughness and workability. Therefore, the Si content is preferably 3.0% by mass or less.

  Mn softens the parent phase, but if it is contained in excess of 3.0% by mass, corrosion resistance may be reduced. Therefore, the content of Mn is preferably 3.0% by mass or less.

  Cr is an important element for maintaining the corrosion resistance, but if it is contained in excess of 30.0% by mass, there is a possibility of inhibiting the manufacturability and workability. Therefore, the content of Cr is preferably 11.0% by mass or more and 30.0% by mass or less.

  Ni softens the parent phase, but if it is contained in excess of 10.0% by mass, the austenite phase may be stabilized and the magnetizing force may be reduced. Therefore, the Ni content is preferably 10.0% by mass or less.

  N increases the strength in the same manner as C. However, if it exceeds 0.50 mass%, N is likely to reduce manufacturability and form Cr nitride to reduce corrosion resistance. . Therefore, the N content is preferably 0.50% by mass or less.

  In addition to the above elements, 7.0% by mass or less of Al (aluminum), 0.8% by mass or less of Nb (niobium), and 0.8% by mass or less of Ti (titanium) Stainless steel containing at least one of Mo (molybdenum), Cu (copper), and W (tungsten) is preferable so that the content is 4.0% by mass or less.

Al improves corrosion resistance, and by performing bright annealing, an oxide film of Al ₂ O ₃ is formed on the surface of stainless steel, thereby improving the reflectance. However, if it is contained in excess of 7.0% by mass, productivity may be impaired. Therefore, the content of Al is preferably 7.0% by mass or less.

  Nb and Ti improve strength and corrosion resistance by forming carbides and nitrides. However, if the content exceeds 0.8% by mass, the manufacturability may decrease. Therefore, the Nb and Ti contents are each preferably 0.8% by mass or less.

  Mo, Cu, and W improve strength, but if their total content exceeds 4.0% by mass, the productivity may decrease. Therefore, it is preferable to contain at least one of Mo, Cu, and W so that the total content is 4.0% by mass or less.

  Next, a method for manufacturing the light reflecting unit 1 will be described.

  When manufacturing the light reflecting unit 1, the magnet sheet 15 is disposed on the concave arc surface of the curved support member 7 of the frame 3.

  Both ends in the longitudinal direction of the reflector 4 formed of a magnetic material such as stainless steel are adsorbed by the magnetic force of the magnet sheet 15 to fix the reflector 4 to the curved support member 7.

  Further, by fixing the reflecting plate 4 in this way, the entire reflecting plate 4 is curved in a concave arc shape along the concave arc surface of the curved support member 7.

  Further, the heat collecting tube 2 is attached to the frame 3 via the support tube member 14 attached to the support plate member 8. The heat collecting tube 2 attached in this way is held in a state facing the reflecting concave arc surface 16 of the reflecting plate 4 so that the reflected light from the reflecting plate 4 is condensed on the heat collecting tube 2.

  Here, it is preferable that the stainless steel used for the reflecting plate 4 has a surface roughness Ra of 0.2 μm or less by high gloss rolling or mirror polishing.

  Further, the stainless steel is preferably subjected to bright annealing at a temperature of 700 ° C. or higher after high gloss rolling or mirror polishing so that the reflectance of light having a wavelength region of 600 nm to 1000 nm is 60% or higher.

  Next, the effect of the one embodiment will be described.

  According to the light reflecting unit 1, the reflecting plate 4 curved in a concave arc shape is fixed to the curved support member 7 by the magnetic force of the magnet sheet 15 and is attached to the frame 3. As described above, it is not necessary to screw the screws and fix them in the form of dots, and it is possible to prevent plastic deformation of the reflecting plate 4 when the reflecting plate 4 is attached to the frame 3. Therefore, the reflector 4 is less likely to be distorted, and the reflectance of the reflector 4 is unlikely to decrease.

  Further, since the reflector 4 is fixed to the curved support member 7 by the magnetic force of the magnet sheet 15, the reflector 4 can be easily attached to and detached from the frame 3.

  Further, since the reflecting plate 4 is formed of stainless steel having a thickness of 0.5 mm or less, when the reflecting plate 4 is bent along the bending support member 7, the reflecting plate 4 is bent within the elastic deformation region. Therefore, the reflector 4 is hardly distorted.

  Furthermore, the stainless steel used for the reflecting plate 4 can improve the reflectance of the reflecting plate 4 by high gloss rolling or mirror polishing so that the surface roughness Ra is 0.2 μm or less.

  Moreover, the stainless steel used for the reflecting plate 4 is subjected to bright annealing at a temperature of 700 ° C. or higher after high gloss rolling or mirror polishing, so that the reflectance of the reflecting plate 4 with respect to light in a wavelength region of 600 nm or more and 1000 nm or less. Can be improved to 60% or more.

  Furthermore, by providing the support plate member 8 on the frame 3, not only the heat collecting tube 2 can be held at an appropriate position, but also the corners at the end portions in the width direction of the reflection plate 4 are supported. Therefore, the position shift of the reflecting plate 4 can be prevented.

  In the above embodiment, the curved support member 7 is provided at both ends of the rod-shaped support member 6, and only the both ends in the longitudinal direction of the reflector 4 are attracted to the magnet sheet 15 by the curved support member 7. However, the present invention is not limited to such a configuration, and at least a part of the reflecting plate 4 is attracted by the magnetic force of the magnet sheet 15, so that the reflecting plate 4 is curved in a concave arc along the bending support member 7. If it is the structure attached to the frame 3 in the state, the number, position, and size of the bending support member 7 and the magnet sheet 15 can be designed as appropriate.

  Further, although the magnet sheet 15 is provided as the magnetic attracting portion, the present invention is not limited to such a configuration, and the magnetic attracting portion may be any configuration that has a magnetic force and can attract the magnetic material.

  Further, in addition to the so-called trough-type light reflecting unit as in the above-described embodiment, a so-called tower in which a so-called Fresnel-type light reflecting unit having a long distance between the heat collecting tube and the reflecting plate or a flat reflector is combined. It can also be applied to a type of light reflection unit.

  Hereinafter, this example and a comparative example will be described.

  Test steels having chemical components shown in Table 1 were melted by 30 kg of vacuum melting and used as a material for a reflector in this example and comparative example.

  A steel plate having a thickness of 30 mm was cut out from each molten steel ingot, heated at 1230 ° C. and soaked, and then hot worked to obtain a 4.5 mm hot rolled plate. Moreover, about this hot-rolled sheet, 800-1100 degreeC annealing and cold rolling were repeatedly performed, and it was set as the 0.2-0.8-mm cold-rolled sheet and the cold-rolled annealed sheet. In addition, the rolled material of these cold-rolled sheets and cold-rolled annealed sheets was adjusted so that Ra on the surface was in the range of 0.02 to 0.50 μm by changing the roughness of the rolling roll.

  In addition to the cold rolling, by adjusting the buff polishing amount and mirror polishing, Ra was changed similarly to the rolled material to obtain an abrasive.

  Furthermore, the rolled material was annealed at 800 to 1100 ° C. in a 93% hydrogen atmosphere to give a bright annealed finish to obtain a bright annealed material.

  And about these rolling materials, abrasives, and bright annealing materials, while evaluating magnetic adsorption property, the reflectance was measured. Table 2 shows the results of these magnetic adsorption properties and reflectivity.

  For magnetic adsorption, a commercially available magnet sheet having a thickness of 1.0 mm is curved to R100 mm, and the reflecting plate is adsorbed. Was evaluated as x.

For the reflectance, the glossiness was measured using a spectrophotometer, and the reflectance for light having wavelengths of 600 nm and 1000 nm was measured according to JIS Z8741. The reflectance was evaluated based on a relative reflectance of 60%, with the reflectance of a standard white plate of Al ₂ O ₃ being 100%.

  As shown in Table 2, when the plate thickness was 0.5 mm or less, no positional deviation occurred even when magnetically attracted in a curved state, and the magnetic attractability was good.

  Moreover, the surface roughness Ra of 0.2 μm or less was good at a reflectance of 60% or more at both wavelengths of 600 nm and 1000 nm.

  Next, the light reflecting unit 1 having the configuration shown in FIG. 1 was produced, and a heating / cooling test was performed assuming long-term use.

  Specifically, a small light reflection unit 1 having a diameter corresponding to the length in the longitudinal direction of the support plate member 8 of 80 mm and a length of the rod-shaped support member 6 of 200 mm is prepared and heated at 300 ° C. in advance. The process of charging in a tubular furnace (electric furnace) for 5 minutes and then removing for 5 minutes was repeated 10,000 times. In these steps, since the maximum temperature of the light reflection unit 1 is 200 ° C., a heat-resistant magnet sheet is used as a magnetic adsorption part for the acceleration test. Moreover, as the reflecting plate 4, the rolled material of A6 in Table 2 was used.

  The heat collection efficiency change by the light reflection unit 1 is measured by irradiating the reflective concave arc surface 16 of the reflector 4 with a commercially available halogen heater for 1 hour, and then measuring the temperature rise of water as the fluid supplied into the heat collection tube 2. The temperature increase rate after the heating / cooling test was calculated by dividing by the temperature increase rate before the heating / cooling test. The results are shown in Table 3.

  Moreover, what used the rolled material of A5 in Table 2 as a reflecting plate 4 was made into the comparative example, and the weekly thermal efficiency change was measured similarly. Furthermore, as a comparative example, in the configuration in which the Al reflector 4 is attached to the frame 3 by bolt fastening, and in the configuration in which the Al reflector 4 is attached to the frame 3 with an adhesive, the heat collection efficiency changes. It was measured. These results are shown in Table 3.

  As shown in Table 3, No. In No. 1, the heat collection efficiency did not substantially decrease even after the heating / cooling test.

  On the other hand, No. which is a comparative example having a plate thickness greater than 0.5 mm. In No. 2, the heat collection efficiency was lowered. This is thought to be due to the occurrence of misalignment due to poor magnetic adsorption.

  Moreover, No. which is a comparative example in which the reflector 4 is fixed by bolt fastening. No. 3 also had a reduced heat collection efficiency. This is thought to be due to loosening of the bolt due to repeated heating and cooling.

  In addition, No. which is the comparative example which fixed the reflecting plate 4 with the adhesive agent. No. 4 could not measure the change in heat collection efficiency because the adhesive deteriorated and peeled during heating.

DESCRIPTION OF SYMBOLS 1 Light reflection unit 2 Heat collecting tube 3 Frame 4 Reflecting plate 7 Curved support member
15 Magnet sheet as magnetic adsorption part

Claims (8)

A light reflecting unit that reflects light to a heat collecting tube through which fluid can flow;
A frame having a curved support member curved in a concave arc shape;
A magnetic attracting portion provided on the curved support member and having a magnetic force;
A reflector made of a magnetic material,
The reflector is attached to the frame in a state of being bent in a concave arc along the curved support member by being attracted by the magnetic force of the magnetic attracting portion, and reflects light to the heat collecting tube. unit. The reflecting plate is made of stainless steel having a thickness of 0.5 mm or less, containing 11% or more of Cr by mass and having soft magnetic properties,
2. The light reflecting unit according to claim 1, wherein the stainless steel is high-gloss rolled or mirror-polished and has a surface roughness Ra of 0.2 μm or less. Stainless steel is in mass%, C: 0.08% or less, Si: 3.0% or less, Mn: 3.0% or less, Cr: 11.0% or more and 30.0% or less, Ni: 10.0 % Or less, N: 0.50% or less is contained, and the balance consists of Fe and unavoidable impurities. The stainless steel contains, by mass%, Al: 7.0% or less, Nb: 0.8% or less, Ti: 0.8% or less, and Mo so that the total content is 4.0% or less. The light reflection unit according to claim 3, comprising at least one of Cu, W, and Cu. 5. The light according to claim 4, wherein the stainless steel is brightly annealed at a temperature of 700 ° C. or higher after high gloss rolling or mirror polishing, and has a light reflectance of 60% or more in a wavelength region of 600 nm or more and 1000 nm or less. Reflective unit. A method of manufacturing a light reflecting unit that reflects light to a heat collecting tube through which fluid can flow,
A magnetic support part having a magnetic force is provided on the curved support member curved in a concave arc shape in the frame,
By attaching the reflector made of a magnetic material with the magnetic force of the magnetic adsorption part, the reflector is attached to the frame so that it bends in a concave arc along the curved support member and reflects light to the heat collecting tube. A method for producing a light reflecting unit. The reflector is stainless steel with soft magnetic properties,
The method of manufacturing a light reflecting unit according to claim 6, wherein the stainless steel is subjected to high gloss rolling or mirror polishing so that the surface roughness of the stainless steel is 0.2 μm or less in terms of Ra. Stainless steel
8. The light according to claim 7, wherein bright annealing is performed at a temperature of 700 ° C. or higher after high gloss rolling or mirror polishing so that the reflectance of light having a wavelength region of 600 nm to 1000 nm is 60% or more. A manufacturing method of the reflection unit.

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