CN201344669Y - Solar high-temperature vacuum heat-collecting tube - Google Patents

Abstract

The utility model relates to a high-temperature vacuum heat collecting tube used in a trough solar thermoelectric system, which comprises a glass outer tube and a metal inner tube installed in the glass outer tube, the glass outer tube is sealed and connected with the metal inner tube, and the interlayer is vacuum , which is characterized in that a ceramic heat insulating ring is arranged between the glass outer tube and the two ends of the metal inner tube. Both ends of the ceramic heat insulating ring are covered with a metallized layer or each has an annular groove, and are sealed and connected to the glass outer tube through an alloy component connected to or embedded in the metallized layer at one end, and the other end is connected to the metal inner tube through a transition connection plate. Or the metallized layer is connected or embedded with a fixed alloy component, and the transition connection plate is sealed and connected with the metal inner tube. The ceramic heat insulating ring provided by the utility model can not only eliminate the "thermal bridge" between the glass outer tube and the metal inner tube, block the heat conduction between the two tubes, and effectively improve the working efficiency of the heat collecting tube, but also the utility model has a simple structure, The production cost is low, and the production bottleneck of the high-temperature vacuum heat collecting tube used in the trough solar thermoelectric system can be overcome, and the development of the solar thermoelectric technology and its application can be effectively promoted.

Description

Solar High Temperature Vacuum Heat Collector

technical field

The utility model belongs to the technical field of solar heat energy utilization devices, and relates to a vacuum heat collector for absorbing solar heat energy, in particular to a high-temperature vacuum heat collection tube used in a trough solar thermoelectric system.

Background technique

In solar thermal energy utilization technology, thermal power generation technology can significantly improve the utilization efficiency of solar thermal energy, especially trough solar thermal power generation device, which is considered to be the most practical technology in solar thermal power technology. The trough solar thermal power generation system uses a trough parabolic concentrator to gather sunlight and heat to the heat collecting element located on the focal line of the trough parabolic. The heat collecting element is generally a tubular heat absorber (heat collector) , the fluid working substance inside the tube, after being heated by the converted solar energy, flows through the heat exchanger to heat the working substance, converts it into high-temperature and high-pressure hot steam, and then generates electricity with the help of steam cycle power.

Most of the tubular heat absorbers currently used are vacuum heat collectors. Its typical structure includes a metal inner tube coated with a heat-absorbing material layer and a glass outer tube installed outside the inner tube. The two are fixed and make the glass outer tube and The interlayer between the metal inner tubes is vacuum. The vacuum layer can improve the thermal insulation effect of the metal inner tube, so that the solar heat accumulated in the metal inner tube can be transferred to the working material in the tube as much as possible, so as to improve the working efficiency of the vacuum heat collecting tube. However, the sealing between glass and metal has always been a technical difficulty that needs to be overcome in the vacuum industry and the solar energy industry, and has always been a research hotspot in the vacuum industry and the solar energy industry. Therefore, various sealing methods have also been developed. Such as using hot pressing or magnetic pulse hot pressing to seal. Due to the difference in thermal expansion between the glass outer tube and the metal inner tube in the heat collecting tube, in the case of a large temperature change, the directly fused glass outer tube and metal inner tube will easily break the glass, resulting in the destruction of the entire structure. Moreover, due to the difference in chemical bonds between glass and metal atoms and molecules, it is difficult to seal the two. In order to solve these problems, CN1266824 and CN1266824 disclose ways to connect through transition members, such as Kovar or support rings and bellows. These means solve the connection problem between the metal tube and the glass tube to a certain extent, prolong the life of the vacuum tube, improve the heat preservation efficiency and service temperature of the vacuum tube, and reduce the cost. However, since the transition components used are all metal materials, a "thermal bridge" for rapid heat transfer will be formed, causing a large amount of heat to be lost, reducing the solar heat accumulated in the metal inner tube and transferred to the working material in the tube, and greatly reducing the efficiency of the heat collecting tube. Work efficiency makes this type of heat collecting tube only applicable to low-temperature solar energy utilization fields such as solar water heaters.

In the field of solar thermal power generation, the thermal working fluid in the heat collecting tube must be heated above 350°C to have practical application value. Apparently, the above heat collecting tubes connected by metal cannot meet the requirements of use due to the large loss of heat. Even if various strengthening technical measures can be used to heat the thermal working medium in the heat-collecting metal tube to above 350°C, and because the working temperature of the glass outer tube is room temperature or slightly higher than room temperature, on the one hand, it is very difficult to keep warm under such a large temperature difference. Difficult, generally need to draw a high vacuum between the two lumens, on the other hand, under such a large temperature difference, the speed of heat conduction will be more powerful, and the heat loss will be greater. It is precisely because of the above reasons that the high-temperature vacuum heat collection tubes used in trough solar thermal power systems have not been well resolved, and seriously restrict the development of solar thermal power technology.

Chinese patent application 200410014676.2 discloses a high-temperature vacuum heat collecting tube. This application does not directly weld the metal tube and the glass tube through the transition member, but uses nuts, high-temperature-resistant seals and top nuts to connect the interface of the metal bellows to the vacuum The outer wall of the annular heat-insulation cavity is firmly sealed, and the other port of the metal bellows is welded with the glass tube by transition material Kovar alloy. The vacuum annular heat insulation chamber can play a role of heat insulation transition to a certain extent, thereby reducing the temperature at the glass nozzle and improving the reliability of the high-temperature vacuum heat collection tube. However, since the vacuum annular heat insulation chamber is still made of metal, Therefore, on the one hand, the "thermal bridge" between the glass tube and the metal tube still exists, and on the other hand, the structure of the heat insulation cavity is complicated, and the manufacturing cost is high.

Contents of the invention

In view of the deficiencies in the prior art of vacuum heat collecting tubes, the purpose of this utility model is to provide a solar high-temperature vacuum heat collecting tube that eliminates the "thermal bridge" between the glass outer tube and the metal inner tube and effectively improves the working efficiency.

The purpose of this utility model can be realized by the high-temperature vacuum heat collecting tube with the following technical solutions:

The solar high-temperature vacuum heat collection tube includes a glass outer tube and a metal inner tube installed in the glass outer tube. The glass outer tube and the metal inner tube are sealed and connected, and the interlayer is vacuum. It is characterized in that the glass outer tube and the metal inner tube A ceramic heat insulating ring is arranged between the two ends of the tube.

Because the ceramic used in the utility model has good thermal insulation performance, it can eliminate the "thermal bridge" between the glass outer tube and the metal inner tube, block the heat conduction between the two tubes, improve the thermal insulation performance of the metal inner tube, and benefit the metal The inner tube transmits as much heat as possible to the working substance, effectively improving the working efficiency.

As an optimal solution for the connection of the ceramic insulation ring with the glass outer tube and the metal inner tube, the two ends of the ceramic insulation ring are covered with a metallization layer, and the ceramic insulation ring is sealed with the glass outer tube through an alloy member connected to the metallization layer at one end. The other end is sealed and connected with the metal inner tube through a transition connection plate or through the alloy component connected on the metallized layer, and the transition connection plate and the metal inner tube.

As another preferred solution for the connection of the ceramic insulation ring with the glass outer tube and the metal inner tube, an annular groove is opened on both ends of the ceramic insulation ring, and an alloy component is embedded and fixed in it, and the other end of the alloy component is respectively connected to the glass outer tube. The tube is sealed and connected with the metal inner tube through a transition connection plate.

The alloy component described in the above scheme is an alloy ring made of Kovar alloy; the connection method is specifically welding or welding. Before connecting, vitrify the connection surface of the Kovar alloy ring, or carry out metallization treatment on the connection surface of the glass outer tube, so as to increase the connection strength between the two.

Because the metal inner tube in the heat collecting tube of the present invention will inevitably expand when heated, and shrink again after cooling down, especially the longitudinal thermal expansion rate of the metal tube is far greater than that of the glass tube. Therefore, in the glass outer tube A metal bellows is also arranged between the metal inner tube, and the metal bellows is located between the alloy component and the transition connection plate or connected to one end of the glass outer tube. Because the metal bellows has good axial flexibility, it can effectively solve the problem of damage to the vacuum heat collecting tube due to the difference in thermal expansion and contraction between the metal inner tube and the glass outer tube.

In order to better realize the application purpose of the utility model, the utility model can also take the following technical measures:

The material of the ceramic ring is vacuum electronic ceramics such as aluminum oxide, so as to reduce the thermal conductivity and thermal expansion coefficient as much as possible.

The outer surface of the ceramic ring is covered with a layer of enamel to ensure good vacuum tightness of the ceramic ring.

The metal inner tube is made of stainless steel, so that the steel tube has high mechanical strength and high thermal conductivity, and the outer surface of the steel tube is coated with a coating that can enhance solar energy absorption, such as a black body absorbing coating that is selective to solar energy. layer material. The coating can be plated on the steel pipe by vacuum sputtering, magnetron sputtering, chemical deposition and other methods.

The glass outer tube is made of high boron glass with high light transmittance, excellent weather resistance and high mechanical strength, its inner wall is coated with an antireflection film, and the outer wall is coated with an antireflection protective film with excellent weather resistance. The anti-reflective protective film also has a self-cleaning function.

Both ends of the heat collecting tube are provided with a protective end cap, which can protect the end of the heat collecting tube from being burned by light and heat gathered by the reflective surface. The end cap is made of metal material, and its inner surface can be coated with a Layer insulation.

If the long diameter of the high-temperature vacuum heat collecting tube is relatively large, at least one support ring is also arranged between the vacuum interlayer of the glass outer tube and the metal inner tube, and the support ring is fixed on the steel pipe to ensure heat resistance and heat insulation. They are all made of good ceramic materials, and the support ring has at least two blind holes in the radial direction, and springs are placed in the holes to buffer the radial extrusion force on the glass outer tube when the steel tube is heated and expands radially.

The outer surface of the metal inner tube is provided with a vacuum degree color band, which can not only absorb a small amount of gas in the vacuum interlayer, but also serve as an indicator mark of the vacuum degree change of the vacuum interlayer.

In order to facilitate the vacuuming of the interlayer between the metal inner tube and the glass outer tube of the heat collecting tube, a glass branch tube can be pre-connected to the glass outer tube, and the branch tube can be welded and sealed after vacuuming; it can also be placed on the exposed part of the Kovar alloy ring A kovar alloy branch pipe is preset, and the branch pipe is melt-sealed after vacuuming.

The insulating ceramic ring, kovar alloy ring, bellows, protective end cap and other components can be lined with a heat insulating material ring between the metal inner pipe to reduce the heat transfer of the inner steel pipe to the outside. The heat insulating material ring can It is made of mica, asbestos, ceramics and other high temperature resistant heat insulation materials.

Compared with the existing solar vacuum heat collecting tube, the utility model has the following outstanding technical effects:

1. Because the ceramic ring provided between the glass outer tube and the metal inner tube in the utility model has good thermal insulation performance, it not only eliminates the "thermal bridge" formed by the metal transition member, but also blocks the gap between the two tubes. Excellent heat conduction improves the thermal insulation performance of the metal inner tube, which is beneficial for the metal inner tube to transmit as much heat as possible to the working material, effectively improving work efficiency.

2. Since the heat-insulating ceramic ring adopted in the utility model blocks the heat conduction between the glass outer tube and the metal inner tube, a large temperature difference between the inner and outer tubes can be maintained for a long time, ensuring that the metal inner tube can be kept at a temperature above 350°C work at high temperatures.

3. The utility model is simple in structure and low in production cost, overcomes the production bottleneck of the high-temperature vacuum heat collecting tube used in the trough solar thermoelectric system, and can effectively promote the development of solar thermoelectric technology and its application.

Description of drawings

FIG. 1 is a schematic diagram of the overall structure of the vacuum heat collecting tube in Embodiment 1 of the present invention.

Fig. 2 is an enlarged schematic diagram of a local structure of one end of the vacuum heat collecting tube in Embodiment 1 of the present utility model.

Figure 3 is an enlarged schematic view of the partial structure of one end of the vacuum heat collecting tube in Example 2 of the present invention

Fig. 4 is an enlarged schematic diagram of a local structure of one end of the vacuum heat collecting tube in Embodiment 3 of the present invention.

Detailed ways

Provide the embodiment of the utility model below in conjunction with accompanying drawing description, and the utility model is described in further detail through the embodiment.

Example 1

As shown in Fig. 1 and Fig. 2, the high-temperature vacuum type heat collecting tube provided in this embodiment is mainly composed of a metal inner tube 1, a glass outer tube 3, a ceramic heat insulating ring 4, a Kovar alloy ring 7, a metal bellows 11, and a transition connection Disk 12 and protective end cap 15 constitute.

The metal inner tube 1 is a stainless steel tube coaxially sheathed in the glass outer tube 3, and the outer surface of the steel tube is covered with a black body absorbing coating material which is selective to solar energy. The glass outer tube 3 is made of high boron glass, its inner wall is plated with an anti-reflection film, and the outer wall is plated with an anti-reflection protective film. The glass outer tube 3 and the metal inner tube 1 are hermetically connected, and the interlayer is vacuum. The outer surface of the stainless steel tube 1 in the interlayer is also spot-welded with a vacuum color display band 16 that can absorb air, which can be used as an indicator mark of the vacuum degree change of the vacuum interlayer, and can absorb a small amount of gas in the vacuum interlayer. There are two ceramic heat insulating rings 4, which are respectively sleeved between the metal inner tube 1 and the two ends of the glass outer tube 3. The ceramic heat insulating ring 4 is a vacuum electronic ceramic made of Al2O3 material, and its two ends are metallized so that it is covered with a metallized layer 5 . In order to prevent the gas from infiltrating into the vacuum interlayer through the small holes on the outer surface of the ceramic heat insulating ring 4, an enamel layer 6 is sintered on the outer surface, and there is no gap between the enamel layer and the metallized layer on the end face to ensure the gas of the ceramic ring. Tightness. Kovar ring 7 has a concave cross-sectional shape, and is connected to glass outer tube 3 and ceramic heat insulating ring 4 through its outer ring surface and inner concave surface respectively. Its specific connection method can be welding or welding. In order to increase the connection strength between the two, the outer ring surface of the Kovar alloy ring 7 can be vitrified before the connection, or the inner connection surface of the glass outer tube 3 can be metallized. The metal bellows 11 is located between the Kovar ring 7 and the transition connection plate 12 . The transition connection plate 12 in this embodiment is a flange, which is welded on the metal inner pipe 1 . There are two protective end caps 15, which are made of metal materials, and their inner surfaces are coated with a layer of heat insulating material. The light and heat gathered by the reflective surface burned. In addition, a thermal insulation pad 2 made of mica is placed between the protective end cap 15 and the contact portion of the ceramic thermal insulation ring 4 and the metal inner tube 1 to reduce the heat transfer of the metal inner tube to the outside.

Considering that when the long diameter of the heat collecting tube is relatively large, the strength of the glass outer tube 3 will be affected to a certain extent. In this embodiment, a support ring 13 is arranged in the vacuum interlayer of the glass outer tube 3 and the metal inner tube 1. The support ring 13 It is fixed on the metal inner tube 1 and made of ceramic material with good heat resistance and heat insulation, and the support ring 13 has at least two blind holes in the radial direction, and a spring 14 is placed in the hole to buffer the metal inner tube. The radial extrusion force on the glass outer tube 3 when the tube 1 is heated and expands radially.

This embodiment is suitable for vacuum heat collecting tubes with small size and small length-to-diameter ratio.

Example 2

As shown in Figure 3, the high-temperature vacuum heat collector provided in this embodiment is also mainly composed of a metal inner tube 1, a glass outer tube 3, a ceramic insulation ring 4, Kovar rings 7-8, a metal bellows 11, and a transition connection Disk 12 and protective end cap 15 constitute.

Due to the structure and production materials of the metal inner tube 1, the glass outer tube 3, the ceramic heat insulating ring 4, the Kovar ring 7, the metal bellows 11, the transition connection plate 12 and the protective end cap 15 of the present embodiment, including the The supporting ring 13 etc. are all the same as in Embodiment 1, so they are omitted. The difference is that a Kovar alloy ring 8 is added between the heat insulating ceramic ring 4 and the metal bellows 11 . The cross section of the Kovar ring 8 is "π"-shaped, and its "π"-shaped upper end surface is welded to the ceramic heat insulating ring 4, and its lower outer surface is welded to one end of the metal bellows 11. In this embodiment, the Kovar alloy ring 7 connected to the glass outer tube 3, the ceramic heat insulating ring 4 and the Kovar alloy ring 8 connected to the metal bellows 11 can be welded to form a prefabricated part, and then the next step of connection is performed.

This embodiment is suitable for vacuum heat collecting tubes with relatively long tube diameters and relatively large length-to-diameter ratios.

Example 3

As shown in 4, the high-temperature vacuum heat collector provided in this embodiment is also mainly composed of a metal inner tube 1, a glass outer tube 3, a ceramic insulation ring 4, a Kovar alloy ring 9-10, a metal bellows 11, and a transition connection plate 12 and protective end cap 15 constitute.

Due to the structure and manufacturing materials of the metal inner tube 1, the glass outer tube 3, the ceramic insulation ring 4, the metal bellows 11, the transition land 12 and the protective end cap 15 of the present embodiment, including the supporting ring 13 provided therein, etc. Same as Example 1, so it is omitted. The difference is: ① In this embodiment, a Kovar alloy ring 10 is added between the heat insulating ceramic ring 4 and the metal bellows 11; ② The cross-sectional shape of the Kovar alloy ring 9 connected to the glass outer tube 3 is that On the basis of the concave shape, there is a protrusion extending from the end of the inner ring surface, which is parallel to the extension protrusion of the outer ring surface; ③ When making the heat-insulating ceramic ring 4, firstly open an annular groove on each of the two ends , and then the two shapes of ① and ② Kovar alloy rings 9, 10 are respectively embedded therein, and then sintered and fixed. In this embodiment, the Kovar alloy ring 9 connected to the glass outer tube 3, the ceramic heat insulating ring 4 and the Kovar alloy ring 10 connected to the metal bellows 11 can also be welded first to form a prefabricated part, and then the next step of connection is performed. .

This embodiment is suitable for vacuum heat collecting tubes with longer tube diameters (4 meters and above) and larger aspect ratios.

The embodiments of the present utility model have been described in detail above in conjunction with the accompanying drawings. Various changes can also be made to the disclosed content and the scope of knowledge possessed, so the specific implementation methods of the present utility model should not be understood as limiting the protection scope of the present utility model.

Claims (10)

1. A solar high-temperature vacuum heat collecting tube, comprising a glass outer tube and a metal inner tube (1) installed in the glass outer tube, the glass outer tube (2) is sealed and connected with the metal inner tube (1), and the interlayer is vacuum, It is characterized in that a ceramic heat insulating ring (4) is arranged between the glass outer tube (2) and the two ends of the metal inner tube (1). 2. The solar high-temperature vacuum heat collection tube according to claim 1, characterized in that the two ends of the ceramic heat insulating ring (4) are covered with a metallized layer (5), and the ceramic heat insulating ring (4) passes through one end of the metallized layer (5) The alloy component (7) connected on the top is sealed and connected with the glass outer tube (3), and the other end is connected to the metal inner tube (1) or the alloy component ( 8), the transition connection plate (12) is sealed and connected with the metal inner tube (1). 3. The solar high-temperature vacuum heat collection tube according to claim 1, characterized in that an annular groove is opened on both ends of the ceramic heat insulating ring (4), in which an alloy component (9, 10) is embedded and fixed, and through the alloy component The other ends of (9, 10) are hermetically connected to the glass outer tube (3) and are hermetically connected to the metal inner tube (1) via a transition connection plate (12). 4. The solar high-temperature vacuum heat collection tube according to claim 2 or 3, characterized in that the alloy member (7, 8, 9, 10) is an alloy ring made of Kovar alloy. 5. The solar high-temperature vacuum heat collection tube according to claim 1, 2 or 3, characterized in that the outer surface of the ceramic heat insulating ring (4) is covered with an enamel layer (6). 6. The solar high temperature vacuum heat collection tube according to claim 4, characterized in that the outer surface of the ceramic heat insulating ring (4) is covered with an enamel layer (6). 7. The solar high-temperature vacuum heat collection tube according to claim 1, 2 or 3, characterized in that the outer surface of the metal inner tube (1) is covered with a coating that can enhance solar energy absorption; the glass outer tube (3 ) and the metal inner tube (1) are also provided with a metal bellows (11), the metal bellows (11) is located between the alloy components (8, 10) and the transition connection plate (12) or connected to the glass outer tube (3) One end. 8. The solar high-temperature vacuum heat collection tube according to claim 6, characterized in that the outer surface of the metal inner tube (1) is covered with a coating that can enhance solar energy absorption; the glass outer tube (3) and the metal inner tube A metal bellows (11) is also provided between the tubes (1), and the metal bellows (11) is located between the alloy components (8, 10) and the transition connection plate (12) or connected to one end of the glass outer tube (3) . 9. The solar high-temperature vacuum heat collecting tube according to claim 1, 2 or 3, characterized in that a protective end cap (15) is provided at both ends of the heat collecting tube; the glass outer tube (3) and the metal inner tube (1) is also provided with at least one support ring (13), and the support ring (13) has at least two blind holes in the radial direction, and a spring (14) is placed in the hole; the metal inner tube (1) A vacuum degree color display band (16) is arranged on the outer surface. 10. The solar high-temperature vacuum heat collection tube according to claim 8, characterized in that a protective end cap (15) is provided at both ends of the heat collection tube; the glass outer tube (3) and the metal inner tube (1) There is also at least one support ring (13) between them, and the support ring (13) has at least two blind holes in the radial direction, and a spring (14) is placed in the hole; the outer surface of the metal inner tube (1) A vacuum color display band (16) is provided.

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