An internally reflective focusing medium-temperature metal-glass sealed heat collection tube

Abstract

This invention discloses an internally reflecting, focusing, mid-temperature metal-glass sealed solar collector tube, belonging to the field of solar collector tube technology. It includes a reflector and a collector tube body. The collector tube body comprises a glass cover tube and a heat-absorbing metal tube coaxially disposed inside the glass cover tube. Corrugated pipe assemblies are disposed on the outer sides of both ends of the heat-absorbing metal tube, and Kovar rings are disposed between the corrugated pipe assemblies and the glass cover tube. A concentrator is installed on the heat-absorbing metal tube. This invention, through the focusing effect of the reflector and the concentrator, allows the heat-absorbing metal tube to receive high-power-density solar radiation energy even when facing away from the reflector. This solves the problem of severe deformation caused by a large heat exchange temperature difference in the heat-absorbing metal tube, significantly improving the solar energy absorption and utilization rate, helping to increase the heat collection temperature, and meeting the needs of mid-temperature applications.

Description

Technical Field

[0001] This utility model relates to the field of heat collection tubes, and in particular to a medium-temperature metal-glass sealed heat collection tube with internal reflection focusing. Background Technology

[0002] Against the backdrop of increasing global energy shortages and environmental problems, solar energy, as a clean and renewable energy source, has received widespread attention for its development and utilization. Medium-temperature solar thermal utilization has enormous application potential in areas such as industrial heating, building heating, and hot water supply. As the core component of medium-temperature solar thermal utilization devices, the performance of the solar collector tube directly determines the system's efficiency, reliability, and economy.

[0003] For trough solar power systems with high concentration ratios, the heat-absorbing metal tube in a medium-temperature metal-glass sealed collector tube is heated only on the side facing the reflector, while the other side receives almost no heat flow. Under these non-uniform heat flux conditions, the surface temperature of the heat-absorbing metal tube can reach over 400°C, and there is a significant heat transfer temperature difference within the tube wall. The resulting thermal stress exceeds the yield strength of the heat-absorbing metal tube, causing it to endure repeated temperature cycles and frequent deformation during system operation. Ultimately, this leads to surface cracking of the heat-absorbing metal tube, i.e., thermal fatigue. Over the long term, permanent deformation can occur, causing the heat-absorbing metal tube to deviate from the focal line of the concentrator. In severe cases, it can even cause the glass sleeve outside the collector tube to crack, resulting in a significant decrease in heat collection efficiency. The resulting thermal stress cannot be ignored.

[0004] The aforementioned problems have frequently occurred in operating direct steam trough solar thermal power plants, revealing a serious lack of understanding in current design and temperature control, which restricts the large-scale commercial application of this technology.

[0005] Based on this, a medium-temperature metal-glass sealed heat collector tube with internal reflection focusing is proposed. Utility Model Content

[0006] The purpose of this invention is to provide an internally reflective focusing medium-temperature metal-glass sealed heat collector tube to solve the problems in the background art.

[0007] To achieve the above objectives, this utility model provides an internally reflective focusing medium-temperature metal-glass sealed heat collection tube, including a reflector and a heat collection tube body disposed on one side of the reflector. The heat collection tube body includes a glass cover tube and a heat-absorbing metal tube coaxially disposed inside the glass cover tube. Corrugated pipe assemblies are disposed on the outer sides of both ends of the heat-absorbing metal tube, and Kovar rings are disposed between the corrugated pipe assemblies and the glass cover tube. A concentrator is installed on the heat-absorbing metal tube.

[0008] Preferably, the corrugated pipe assembly includes a shielding cylinder, a corrugated pipe, a top cover plate, and a getter mounting plate. The outer surface of the shielding cylinder is welded to the inner surface of the corrugated pipe. The two end faces of the corrugated pipe are respectively welded to the top cover plate and the getter mounting plate. Multiple getter mounting brackets are welded circumferentially to the outer surface of the getter mounting plate, and an indicator bracket is welded directly above the outer surface of the getter mounting plate.

[0009] Preferably, one outer end face of the upper cover plate is welded to the outer end face of the Kovar ring, and a side cover plate is welded to the other outer end face of the upper cover plate.

[0010] Preferably, the glass cover tube is provided with an exhaust port on the outside, and a protective cap is provided on the exhaust port.

[0011] Preferably, the concentrator is either a Fresnel concentrator or a U-shaped concentrator.

[0012] Preferably, the angle between the upper edge of the arc surface of the U-shaped concentrator and the longitudinal section of the glass cover tube and the heat-absorbing metal tube is 0°~15°, and the interval between the arc edge of the U-shaped concentrator and the glass cover tube is set to 5mm~20mm; The angle between the upper edge of the arc surface of the Fresnel concentrator and the longitudinal section of the glass cover tube and the heat-absorbing metal tube is 0°~15°, and the interval between the Fresnel concentrator and the glass cover tube is set to 5mm~20mm.

[0013] Preferably, the heat-absorbing metal tube includes a coated metal tube and a heat exchange inner tube arranged coaxially.

[0014] Preferably, the outer wall of the heat exchange inner tube is provided with a first groove, and the inner wall of the coated metal tube is provided with a plurality of second grooves that are adapted to the first groove. The heat exchange inner tube and the coated metal tube are welded together by a medium.

[0015] Preferably, both the first groove and the second groove are either spiral grooves or annular grooves.

[0016] Preferably, the heat-absorbing metal tube includes a coated metal tube and a plurality of annular heat pipes, the plurality of annular heat pipes being disposed on the inner wall of the coated metal tube by means of clips.

[0017] Therefore, the internal reflection focusing medium-temperature metal-glass sealed heat collector tube of this utility model has the following beneficial effects: (1) In this utility model, the reflector and the concentrator work together. The reflector concentrates the received sunlight onto the surface of the heat-absorbing metal tube inside the medium-temperature metal-glass sealed heat collection tube. The high-density solar radiation energy is received by the concentrator and concentrated onto the opposing surfaces of the heat-absorbing metal tube and the concentrator set inside the glass tube. This allows the side of the heat-absorbing metal tube facing away from the reflector to also receive solar radiation energy with high heat flux density. This solves the problem that the heat-absorbing metal tube is only heated on the side facing the reflector when it is working, while the other side has almost no heat flow and the tube wall has a large heat exchange temperature difference and serious deformation.

[0018] (2) This utility model provides a corrugated pipe assembly at both ends of the heat-absorbing metal tube and a Kovar ring between the corrugated pipe assembly and the glass cover tube. By utilizing the good compatibility between the Kovar ring and the glass and metal and the flexible compensation effect of the corrugated pipe, the air leakage problem at the joint between the glass and the metal is effectively solved, ensuring the vacuum inside the heat collection tube and reducing the loss of heat through gas conduction.

[0019] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present utility model; Figure 2 This is a cross-sectional view of the heat collection tube body in Embodiment 1 of this utility model; Figure 3 This is a side view of the heat collection tube body of Embodiment 1 of this utility model; Figure 4 This is a cross-sectional view of the Fresnel concentrator of Embodiment 1 of this utility model; Figure 5 This is a side view of the Fresnel concentrator of Embodiment 1 of this utility model; Figure 6 This is a schematic diagram of the structure of the bellows assembly according to an embodiment of the present utility model; Figure 7 This is a schematic diagram of the structure of Embodiment 1 of the present invention, in which both the coated metal tube and the heat exchange inner tube are provided with spiral grooves. Figure 8 This is a schematic diagram of the structure of Embodiment 1 of the present invention, in which both the coated metal tube and the heat exchange inner tube are provided with annular grooves. Figure 9 This is a schematic diagram of the structure of Embodiment 2 of the present invention; Figure 10 This is a cross-sectional view of the heat collection tube body in Embodiment 2 of this utility model; Figure 11 This is a side view of the heat collection tube body in Embodiment 2 of this utility model; Figure 12This is a schematic diagram of the U-shaped concentrator in Embodiment 2 of this utility model; Figure 13 This is a schematic diagram of the heat-absorbing metal tube in Embodiment 2 of this utility model; Figure label: 1. Collector tube body; 11. Absorber metal tube; 111. Coated metal tube; 112. Mounting parts; 113. Circular heat pipe; 114. Heat exchange inner tube; 12. Corrugated tube assembly; 121. Shielding cylinder; 122. Top cover plate; 123. Corrugated tube; 124. Getter mounting plate; 125. Getter mounting bracket; 126. Indicator bracket; 13. Side cover plate; 14. Kovar ring; 15. Glass cover tube; 16. U-shaped concentrator; 17. Protective cap; 18. Fresnel concentrator; 2. Reflector. Detailed Implementation

[0021] The technical solution of this utility model will be further described below with reference to the accompanying drawings and embodiments.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this utility model, but not all embodiments.

[0023] Example 1 In this embodiment, the heat-absorbing metal tube 11, composed of a Fresnel concentrator 18, a coated metal tube 111, and a heat exchange inner tube 114, is taken as an example. Specifically, as follows... Figures 1-8 As shown, it includes a reflector 2 and a heat collection tube body 1 disposed on one side of the reflector 2. The heat collection tube body 1 includes a glass cover tube 15 and a heat-absorbing metal tube 11 coaxially disposed inside the glass cover tube 15. The surface of the glass cover tube 15 is coated with an anti-reflection coating, and the heat-absorbing metal tube 11 is a heat-absorbing metal heat-conducting tube.

[0024] Bellows assemblies 2 are provided on the outer sides of both ends of the heat-absorbing metal tube 11. The main function of the bellows assembly 12 is to compensate for the expansion of the heat-absorbing metal tube 11 and the glass cover tube 15, so as to reduce the difference in axial thermal expansion caused by the difference in expansion coefficient and heating intensity during operation. The bellows assembly 12 includes a shielding cylinder 121, a bellows 123, an upper cover plate 122, and a getter mounting plate 124. The outer surface of the shielding cylinder 121 is welded to the inner surface of the bellows 123. The two ends of the bellows 123 are welded to the inner circular surfaces of the upper cover plate 122 and the getter mounting plate 124, respectively. Multiple getter mounting brackets 125 are welded circumferentially on the outer surface of the getter mounting plate 124 for fixing the getter and adsorbing residual gas in the tube to maintain vacuum. An indicator bracket 126 is welded directly above the outer surface of the getter mounting plate 124 for installing a vacuum indicator to monitor the vacuum level in the tube.

[0025] One outer end face of the upper cover plate 122 is fused to the outer end face of the Kovar ring 14, and a side cover plate 13 is welded to the other outer end face of the upper cover plate 122. This structure makes a sealed space between the glass cover tube 15 and the heat-absorbing metal tube 11. Vacuuming the sealed space can form a vacuum interlayer.

[0026] The glass cover tube 15 has an exhaust port on its outside. The vacuum jacket is evacuated through the exhaust port. The exhaust port is sealed with a protective cap 17 to protect the exhaust port from external dust and moisture pollution and maintain the vacuum environment after sealing.

[0027] A Kovar ring 14 is installed between the bellows assembly 12 and the glass cover tube 15. The two ends of the glass cover tube 15 are welded to the Kovar ring 14 using flame sealing technology. The Kovar ring 14 is made of metal. The flame sealing technology involves locally heating the portion of the metal Kovar ring 14 and the glass cover tube 15 to be sealed using a flame, softening the encapsulated portion of the glass cover tube 15 and allowing it to flow onto the surface of the metal encapsulated portion. During cooling, it firmly bonds to the metal surface. In this structure, the bellows 123 compensates for the deformation of the glass and metal caused by thermal expansion and contraction, preventing cracking at the seal. The Kovar ring 14 utilizes its compatibility with the glass and metal to achieve a seal, preventing air leakage. The entire assembly ensures vacuum sealing at both ends of the collector tube and structural stability.

[0028] A concentrator is mounted on the heat-absorbing metal tube 11, and the concentrator is positioned opposite the reflector 2. In this embodiment, the concentrator is a Fresnel concentrator 18, a structure already in the prior art. The Fresnel concentrator 18 is connected to the heat-absorbing metal tube 11 via a mounting member 112 and is coaxially arranged with the heat-absorbing metal tube 11. The Fresnel concentrator 18 can focus sunlight onto the surface of the coated metal tube 111, enhancing heat absorption efficiency. The heat-absorbing metal tube 11 includes a coaxially arranged coated metal tube 111 and a heat exchange inner tube 114. The outer surface of the coated metal tube 111 has a selective absorption film. The mounting member 112 is welded to the outer wall of the coated metal tube 111, and the Fresnel concentrator 18 is mounted on the mounting member 112. The mounting member 112 is an L-shaped metal part with mounting holes to facilitate the installation of the Fresnel concentrator 18 on the coated metal tube 111.

[0029] In this structure, the chord length of the Fresnel concentrator 18 is set using the coaxial longitudinal section of the heat-absorbing metal tube 11 and the glass cover tube 15 as the axial reference plane. The angle between the upper edge of the Fresnel concentrator 18's arc surface and the axial reference plane is between 0° and 15°. The optimal gap between the Fresnel concentrator 18 and the glass cover tube 15 is set between 5mm and 20mm. If the gap is too large, the Fresnel concentrator 18 will not achieve a concentrating effect when placed inside the glass cover tube 15. If the gap is too small, the glass cover tube 15 will not be able to pass through smoothly after the Fresnel concentrator 18 is installed on the heat-absorbing metal tube 11.

[0030] A first groove is provided on the outer wall of the heat exchange inner tube 114, and a plurality of second grooves adapted to the first groove are provided on the inner wall of the coated metal tube 111. The heat exchange inner tube 114 and the coated metal tube 111 are welded together by a medium. Both the first groove and the second groove are either spiral grooves or annular grooves.

[0031] In this embodiment, multiple annular grooves are provided on the inner wall of the coated metal tube 111, and a heat exchange inner tube 114 is provided inside the heat-absorbing metal tube 11, with a distance of 5mm to 10mm between them. Multiple annular grooves are provided on the outer wall of the heat exchange inner tube 114, corresponding one-to-one with the annular grooves on the inner wall of the coated metal tube 111. The coated metal tube 111 and the heat exchange inner tube 114 are coaxially arranged. A working medium is injected into the annular grooves corresponding to the coated metal tube 111 and the heat exchange inner tube 114. After the coated metal tube 111 and the heat exchange inner tube 114 are filled with the working medium, the gaps are welded together. The groove design increases the contact area, and the medium welding strengthens the connection strength and heat conduction efficiency, enabling the heat absorbed by the coated metal tube 111 to be efficiently transferred to the heat exchange inner tube 114. During the transport process, the heat transfer medium inside the heat exchange inner tube 114 transfers heat to the heat exchange inner tube 114. The vaporization of the working medium between the heat exchange inner tube 114 and the coated metal tube 111 enables the coated metal tube 111 wall to be heated evenly.

[0032] In other embodiments, the annular groove can also be configured as a helical groove with a pitch of 80mm to 360mm.

[0033] In other embodiments, Fresnel condenser 18 can be replaced with U-shaped condenser 16.

[0034] Example 2 In this embodiment, the heat-absorbing metal tube 11, composed of a U-shaped concentrator 16, a coated metal tube 111, and a circular heat pipe 113, is taken as an example. The remaining structure is the same as in Embodiment 1, as detailed below. Figures 9-13 As shown, the U-shaped concentrator 16 is welded to the heat-absorbing metal tube 11, and its structure focuses light onto the heat-absorbing area, improving the light absorption effect. The heat-absorbing metal tube 11 includes a coated metal tube 111 and multiple annular heat pipes 113. The U-shaped concentrator 16 has a semi-circular arc shape, and the center point of the arc of the U-shaped concentrator 16 is welded to the outer wall of the coated metal tube 111 along the transverse axis. The arc length of the U-shaped concentrator 16 is set with the longitudinal section of the axis of both the glass cover tube 15 and the heat-absorbing metal tube 11 as the axial reference plane, and the angle between the upper edge of the arc of the U-shaped concentrator 16 and the axial reference plane is 0° to 15°. The distance between the arc edge of the U-shaped concentrator 16 and the glass cover tube 15 is set to 5mm~20mm. If the distance is too large, the U-shaped concentrator 16 will not be able to achieve the concentrating effect when placed inside the glass cover tube 15. If the distance is too small, the glass cover tube 15 will not be able to pass through smoothly after the U-shaped concentrator 16 is welded to the heat-absorbing metal tube 11.

[0035] The spacing of the annular heat pipes 113 is set to 100mm~300mm. If the spacing is too large, the wall of the heat-absorbing metal pipe 11 will be heated unevenly, failing to achieve the desired effect. The annular heat pipe 113 is a ring made of metal tube, and the heat transfer medium is placed inside the annular heat pipe 113. Multiple clips are welded to the surface of the annular heat pipe 113. The annular heat pipe 113 is supported and fixed to the inner wall of the coated metal pipe 111 by the clips, and the clips ensure that the annular heat pipe 113 and the coated metal pipe 111 are in close contact. The outermost diameter of the annular heat pipe 113 is 1-8 mm smaller than the inner diameter of the coated metal pipe 111. During the transport process, the heat-receiving working fluid inside the coated metal pipe 111 transfers heat to the annular heat pipe 113. The annular heat pipe 113 can quickly conduct the heat absorbed by the coated metal pipe 111 to the fluid inside the pipe, thereby increasing the heat exchange rate. The vaporization of the working fluid inside the annular heat pipe 113 causes the annular heat pipe 113 to expand, enabling the pipe wall of the coated metal pipe 111 to achieve uniform heating.

[0036] In other embodiments, the U-shaped condenser 16 can be replaced with a Fresnel condenser 18.

[0037] The working principle of the above embodiments is as follows: When sunlight penetrates the atmosphere and reaches the Earth's surface, it produces radiant energy with a low heat flux density. Direct utilization of this energy would be economically unfeasible. Only by concentrating this low-heat-flux-density radiant energy can it be converted into high-heat-flux-density radiant energy. A solar trough collector utilizes a parabolic reflector 2 to focus a beam of parallel light onto a single point. When sunlight strikes the parabolic reflector 2 of the solar trough collector, which is equipped with a solar tracking device, the reflector 2 focuses the received sunlight onto the surface of the heat-absorbing metal tube 11 inside the medium-temperature metal-glass sealed collector tube. In this way, the collector tube receives high-heat-flux-density solar radiation energy. Through heat transfer between the heat-absorbing metal tube 11 and the medium inside the tube, the flowing medium is heated, thus providing power for production and daily life.

[0038] However, this method (i.e. the traditional method) can only allow the surface of the heat-absorbing metal tube 11 corresponding to the reflector 2 to receive solar radiation energy with high heat flux density, while the side of the heat-absorbing metal tube 11 facing away from the reflector 2 cannot receive solar radiation energy with high heat flux density.

[0039] According to the method of Embodiment 1 or Embodiment 2, a concentrator is installed on the heat-absorbing metal tube 11. The concentrator and the reflector 2 in the two embodiments are set opposite each other. After the reflector 2 concentrates the received sunlight onto the surface of the heat-absorbing metal tube 11 inside the medium-temperature metal-glass sealed heat collector tube, the high-density solar radiation energy is received by the U-shaped concentrator 16 or Fresnel concentrator 18 and continues to concentrate the sunlight onto the opposite surface of the heat-absorbing metal tube 11 and the concentrator set in the glass cover tube 15. This allows the side of the heat-absorbing metal tube 11 facing away from the reflector 2 to also receive high heat flux density solar radiation energy. Through the heat transfer between the heat-absorbing metal tube 11 and the medium inside the tube, the problem of the heat-absorbing metal tube 11 of the medium-temperature metal-glass sealed heat collector tube being heated only on the side facing the reflector when it is working, while the other side has almost no heat flow and the tube wall has a large heat exchange temperature difference and serious deformation is solved.

[0040] Therefore, this utility model adopts an internally reflective focusing medium-temperature metal-glass sealed heat collection tube with the above-mentioned structure. The light is reflected by a reflector and focused by a concentrator to the heat-absorbing metal tube. The coated metal tube absorbs the light energy and converts it into heat energy. This structure allows the side of the heat-absorbing metal tube facing away from the reflector to receive high heat flux density solar radiation energy, thereby solving the problem that the heat-absorbing metal tube is only heated on the side facing the reflector when it is working, while the other side has almost no heat flow and the tube wall has a large heat exchange temperature difference and serious deformation. The heat-absorbing metal tube transfers heat to the fluid inside the tube through the internal structure (heat exchange inner tube or circular heat pipe). The glass cover tube maintains a vacuum environment to reduce heat loss, the corrugated pipe assembly and Kovar ring ensure sealing and structural stability, and the getter and exhaust port work together to maintain the vacuum degree, ultimately achieving efficient and stable medium-temperature heat collection function.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although the utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solution of this utility model, and these modifications or equivalent substitutions cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of this utility model.

Claims

1. A medium-temperature metal-glass sealed heat collector tube with internal reflection focusing, characterized in that: The device includes a reflector and a heat collection tube body disposed on one side of the reflector. The heat collection tube body includes a glass cover tube and a heat-absorbing metal tube coaxially disposed inside the glass cover tube. Corrugated pipe assemblies are disposed on the outer sides of both ends of the heat-absorbing metal tube. Kovar rings are disposed between the corrugated pipe assemblies and the glass cover tube. A concentrator is installed on the heat-absorbing metal tube.

2. The internal reflection focusing medium-temperature metal-glass sealed heat collector tube according to claim 1, characterized in that: The corrugated pipe assembly includes a shielding cylinder, a corrugated pipe, a top cover plate, and a getter mounting plate. The outer surface of the shielding cylinder is welded to the inner surface of the corrugated pipe. The two end faces of the corrugated pipe are respectively welded to the top cover plate and the getter mounting plate. Multiple getter mounting brackets are welded circumferentially to the outer surface of the getter mounting plate, and an indicator bracket is welded directly above the outer surface of the getter mounting plate.

3. The internal reflection focusing medium-temperature metal-glass sealed heat collector tube according to claim 2, characterized in that: One outer end face of the upper cover plate is welded to the outer end face of the Kovar ring, and a side cover plate is welded to the other outer end face of the upper cover plate.

4. The internal reflection focusing medium-temperature metal-glass sealed heat collector tube according to claim 3, characterized in that: The glass cover tube is provided with an exhaust port on the outside, and a protective cap is provided on the exhaust port.

5. The internal reflection focusing medium-temperature metal-glass sealed heat collector tube according to claim 4, characterized in that: The concentrator is either a Fresnel concentrator or a U-shaped concentrator.

6. The internal reflection focusing medium-temperature metal-glass sealed heat collector tube according to claim 5, characterized in that: The heat-absorbing metal tube includes a coated metal tube and a heat exchange inner tube arranged coaxially.

7. The internal reflection focusing medium-temperature metal-glass sealed heat collector tube according to claim 6, characterized in that: The outer wall of the heat exchange inner tube is provided with a first groove, and the inner wall of the coated metal tube is provided with a plurality of second grooves that are adapted to the first groove. The heat exchange inner tube and the coated metal tube are welded together by a medium.

8. The internal reflection focusing medium-temperature metal-glass sealed heat collector tube according to claim 7, characterized in that: Both the first groove and the second groove are either spiral grooves or annular grooves.

9. The internal reflection focusing medium-temperature metal-glass sealed heat collector tube according to claim 5, characterized in that: The heat-absorbing metal tube includes a coated metal tube and multiple annular heat pipes, which are mounted on the inner wall of the coated metal tube by clips.

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