CN104075472B - Medium-temperature straight-through all-glass vacuum heat collecting tube - Google Patents

Abstract

The invention relates to a medium-temperature straight-through all-glass vacuum heat collecting tube, which consists of a glass outer tube (1), a glass inner tube (2), a first wave-shaped expansion joint (3(A)), a second wave-shaped expansion joint (3(B) )), the first metal connecting pipe (9(A)) and the second metal connecting pipe (9(B)); one end of the glass outer pipe (1) passes through the first transitional connecting ring (6(A)) and the first One end of the wave expansion joint (3(A)) is sealed, and the other end is sealed with one end of the second wave expansion joint (3(B)) through the second transition coupling ring (6(B)); the other end of the wave expansion joint One end is sealed to both ends of the glass inner tube (2) through a transitional coupling ring; the first metal connecting tube (9(A)) and the second metal connecting tube (9(B)) are respectively welded to the first corrugated expansion joint ( 3(A)) and the outer nozzle of the second wave expansion joint (3(B)). The invention has lower cost, less difficulty in sealing, and is suitable for mid-heat utilization systems of solar energy such as industrial heating and thermal energy refrigeration.

Description

A medium-temperature straight-through all-glass vacuum heat collecting tube

technical field

The invention relates to a medium-temperature through-type all-glass vacuum heat collection tube, which is used in a solar energy medium-temperature heat collection system and belongs to the technical field of solar heat utilization.

Background technique

Solar energy medium and high temperature heat utilization technology, including industrial heat, air conditioning and refrigeration, and solar thermal power generation, is a research hotspot. The trough collector is currently the most commercialized solar medium temperature collector. Straight-through metal-glass vacuum collector tubes are the core components of current trough collectors as components to realize light-to-heat conversion. Commercial straight-through metal-glass vacuum heat collectors include UVAC heat collectors produced by Siemens and PTR heat collectors produced by Schott. The metal-glass sealing is relatively difficult, and the key technology of sealing is monopolized by foreign countries. The technical blockade is implemented, and the cost of the heat collecting tube is relatively high. The difference in expansion between the metal tube and the glass tube is the main reason for the failure of the seal of the heat collecting tube. Domestic straight-through metal-glass vacuum heat collectors are still in the imitation stage, have not been applied on a large scale, and their key performance indicators are still behind foreign countries. It is of great significance to develop a high-efficiency, low-cost new straight-through heat collector suitable for solar energy medium-temperature heat utilization systems.

Chinese utility model patents with patent numbers ZL99221202.2 and ZL200520133468.4 both invented a straight-through glass vacuum solar collector tube suitable for solar water heaters. Metal expansion joints are placed on the straight tube sections of the inner glass tube and the outer glass tube. Absorbing the thermal expansion caused by heat, compared with the traditional U-shaped all-glass vacuum heat collecting tube, the heat collecting tube improves the flow mode in the tube and strengthens the heat collecting effect. However, since the nozzles at both ends are glass structures, they cannot be effectively connected in series for large-scale medium-temperature heat collection systems.

The Chinese invention patent with the application number of 200810019640.1 discloses a straight-through all-glass vacuum solar collector tube, and U-shaped expansion joints are used at both ends to eliminate the expansion of the inner and outer glass tubes from the radial direction. However, the heat collecting tube is only used in the CPC (Compound Parabolic Concentrator) concentrating system with low magnification internal concentration, and the heat collecting temperature is low; at the same time, setting the CPC in the vacuum interlayer increases the heat loss of the heat collecting tube.

Wang Ruzhu from Shanghai Jiaotong University proposed a straight-through all-glass vacuum heat collector in the article "Performance investigation on novel single-pass evacuated tube with asymmetrical compound parabolic concentrator" (Solar Energy, 2013, 98: 275-289). The outer tube is a glass tube (expansion joint) with multiple corrugated structures, which is used to compensate the difference in expansion of the inner and outer tubes. Due to the poor toughness of the glass, the corrugated glass structure cannot effectively compensate for the large difference in expansion, and the working temperature is lower than 100°C. In addition, the nozzles at both ends of the heat collecting tube are also of glass sealing structure, which is not convenient for series connection.

Contents of the invention

The purpose of the present invention is to overcome the limitations of the existing straight-through metal-glass vacuum heat collecting tubes and straight-through all-glass vacuum heat collecting tubes, and provide a high-efficiency, low-cost medium-temperature through-through Type all-glass vacuum heat collector.

The technical solution of the present invention is: a medium-temperature straight-through all-glass vacuum heat collecting tube, which consists of a glass outer tube 1, a glass inner tube 2, a first wave-shaped expansion joint 3 (A), a second wave-shaped expansion joint 3 (B), a second wave-shaped expansion joint A metal connecting pipe 9 (A) and a second metal connecting pipe 9 (B); a vacuum space 4 is formed between the glass outer pipe 1 and the glass inner pipe 2, and the outer surface of the glass inner pipe 2 is coated with high absorption rate and low emissivity The selective absorbing coating 8; the side of the outer surface of the glass inner tube 2 near the end is pasted with a getter 5; one end of the glass outer tube 1 passes through the first transition coupling ring 6 (A) and the first corrugated expansion joint 3 ( One end of A) is sealed, and the other end is sealed with one end of the second wave expansion joint 3 (B) through the second transition coupling ring 6 (B); the first wave expansion joint 3 (A) and the second wave expansion joint 3 The other end of (B) is respectively sealed with the two ends of the glass inner tube 2 through the third transition coupling ring 7 (A) and the fourth transition coupling ring 7 (B); the first metal coupling tube 9 (A) and the second The metal connecting pipes 9 (B) are respectively welded to the outer nozzles of the first wave expansion joint 3 (A) and the second wave expansion joint 3 (B).

The material of the above-mentioned glass outer tube 1 and glass inner tube 2 is preferably borosilicate glass; the diameter of the glass inner tube 2 is preferably 30-70mm, and the length is 1-4m; the diameter of the glass outer tube 1 is 10 times larger than that of the glass inner tube 2. ~30mm.

It is preferable that the materials of the above-mentioned corrugated expansion joints are all stainless steel; the form of sealing connection between the corrugated expansion joint and the glass outer tube and glass inner tube is external or built-in; the external type is set outside the glass outer tube 1; the built-in type is set Inside the glass outer tube 1.

Preferably, the wave number range of the corrugated expansion joint is 1 to 10, and the waveform is U-shaped or Ω-shaped. The transition coupling ring is made of stainless steel or an expansion alloy, and the expansion coefficient of the material is 3×10 ^-6 to 12×10 ^-6 m/(m·°C); more preferably, the expansion alloy is Fe-Co-Ni. When cutting alloys, the expansion coefficient is 4×10 ^-6 ~ 6×10 ^-6 m/(m·℃) in the temperature range of 25~400℃.

The sealing method of the glass outer tube and the glass inner tube as well as the wave expansion joint and the transition coupling ring adopts high-frequency electromagnetic induction melting sealing, heat compression sealing or solder welding process.

Preferably, the degree of vacuum of the above-mentioned vacuum space 4 is 5×10 ⁻⁵ to 0.05 Pa.

Preferably, the absorptivity of the selective absorbing coating 8 with high absorptivity and low emissivity mentioned above is 86%-96%, and the emissivity is 4%-14%.

The getter 5 is an evaporable getter, its material is barium aluminum nickel or barium titanium, and its shape is dish, strip, ring or cup.

The metal connecting pipe 9 is made of metal materials such as stainless steel. When multiple medium-temperature straight-through all-glass vacuum heat collecting pipes are connected, they can be connected by direct welding or by welding flanges on the metal connecting pipe 9 .

The medium-temperature straight-through all-glass vacuum heat collection tube is suitable for trough, compound parabolic and Fresnel light concentrating heat collection systems.

According to the data known in the art, all medium-temperature straight-through all-glass vacuum tube heat collectors that are similar in form and material to the present invention without substantial changes fall within the protection scope of the present invention.

Beneficial effect:

(1) The glass outer tube and the glass inner tube material of the present invention are all glass, and the heat collection efficiency of the heat collecting tube is 65% to 85%; compared with the straight-through metal-glass vacuum heat collecting tube, when the working temperature is 100 to 300°C, The thermal stress is reduced by 50% to 80%, thereby reducing the difficulty of sealing and the failure rate, and improving the reliability of the heat collecting tube working under the condition of medium temperature.

(2) The outer tube and the inner tube of the present invention are made of glass material, which not only lowers the material cost, but also reduces the difficulty of sealing and lowers the process cost.

(3) Metal welded tubes are reserved at both ends of the present invention, which facilitates the connection of multiple heat collecting tubes to obtain a higher heat collecting temperature, and is suitable for solar medium heat utilization systems such as industrial heating and thermal energy refrigeration.

Description of drawings

Figure 1 is a schematic diagram of the structure of a medium-temperature straight-through all-glass vacuum heat collector when the U-shaped expansion joint is placed externally;

Among them, 1-glass outer tube; 2-glass inner tube; 3(A)-first wave expansion joint; 3(B)-second wave expansion joint; 4-vacuum space; 5-getter; 6(A )-first transition coupling ring; 6(B)-second transition coupling ring; 7(A)-third transition coupling ring; 7(B)-fourth transition coupling ring; 8-selective absorbing coating; 9 (A) - first metal coupling pipe; 9(B) - second metal coupling pipe.

Figure 2 is a partial view of the connection between the glass outer tube and the glass inner tube when the U-shaped expansion joint is placed externally;

Fig. 3 is a structural schematic diagram of a straight-through double-layer glass vacuum heat collecting tube when a U-shaped internal expansion joint is built in;

Figure 4 is a partial view of the connection between the glass outer tube and the glass inner tube when the U-shaped internal expansion joint is built in.

detailed description

Example 1

As shown in Fig. 1, the present invention discloses a medium-temperature straight-through all-glass vacuum heat collecting tube, which is composed of a glass outer tube 1, a glass inner tube 2, a corrugated expansion joint 3 and a metal connecting tube 9; the glass outer tube 1 and the glass inner tube There is a vacuum space 4 between the tubes 2, and the outer surface of the glass inner tube 2 is coated with a selective absorbing coating 8 with high absorption rate and low emissivity; the outer surface of the glass inner tube 2 is pasted with a getter 5 near the end; One end of the glass outer tube 1 is sealed to one end of the first wave expansion joint 3 (A) through the first transition coupling ring 6 (A), and the other end is connected to the second wave expansion joint 3 (A) through the second transition coupling ring 6 (B) One end of B) is sealed; the other ends of the first wave expansion joint 3 (A) and the second wave expansion joint 3 (B) respectively pass through the third transition coupling ring 7 (A) and the fourth transition coupling ring 7 (B) It is sealed with both ends of the glass inner tube 2; the first metal connecting pipe 9 (A) and the second metal connecting pipe 9 (B) are respectively welded to the first wave expansion joint 3 (A) and the second wave expansion joint 3 ( The outer nozzle of B); the expansion joint 3 adopts an external type, that is, it is placed outside the glass outer tube 1; the diameter of the glass inner tube 2 is 70mm, and the length is 1m; The glass outer tube 1 and the glass inner tube 2 are made of borosilicate glass 3.3. The corrugated expansion joint 3 is made of stainless steel, the wave is U-shaped, and the wave number is 10. The material of transition coupling ring Ⅰ6 and transition coupling ring Ⅱ7 is Fe-Ni expansion alloy with an expansion coefficient of 3×10 ^-6 m/(m·℃), which are respectively bonded to glass outer tube 1, The glass inner tube 2 and the corrugated expansion joint 3 are sealed. The vacuum degree of the vacuum space 4 is 0.05 Pa, the absorption rate of the selective absorption coating is 86%, and the emissivity is 4%. Figure 2 is a partial view of the connection between the glass outer tube and the glass inner tube.

The heat collecting tube in this embodiment is used in a Fresnel type concentrating system, the heat collecting efficiency of the heat collecting tube is 65% to 75%, and the heat collecting temperature range is 0 to 200°C; Metal-glass vacuum heat collectors are reduced by about 50%.

Example 2

As shown in Figure 3, it is another embodiment of the present invention, the described corrugated expansion joint 3 is a built-in type, that is, it is placed inside the glass outer tube 1; the glass inner tube 2 has a diameter of 30mm and a length of 2m; the glass outer tube 1. The diameter is 10mm larger than that of the glass inner tube 2; the material of the glass outer tube 1 and the glass inner tube 2 is borosilicate glass 5.0; the corrugated expansion joint 3 is made of stainless steel, the waveform is U-shaped, and the wave number is 1; the transition connecting ring I6 and the transition The material of the connecting ring Ⅱ7 is Fe-Ni-Co Kovar alloy with an expansion coefficient of 4×10 ^-6 m/(m·℃), and it is connected with the glass outer tube 1 and the glass inner tube 2 respectively by fusion sealing and solder welding. And the corrugated expansion joint 3 is sealed; the vacuum degree of the vacuum space 4 is 0.01Pa; the absorption rate of the selective absorption coating is 96%, and the emissivity is 14%. All the other structural forms are identical with embodiment 1. Fig. 4 is a partial view of the connection between the glass outer tube and the glass inner tube in the form of an internal expansion joint.

The heat collecting tube in this embodiment is used in the trough-type concentrating system, the heat collecting efficiency is 75% to 85%, and the heat collecting temperature range is 0 to 300°C; when the working temperature is 300°C, the thermal stress of the heat collecting tube is higher than that of the straight-through metal-glass vacuum The heat collecting tube is reduced by about 80%.

Example 3

In yet another embodiment of the present invention, the wave-shaped expansion joint 3 is Ω-shaped, and the length of the glass outer tube is 4m; the transition coupling ring I6 and transition coupling ring II7 are made of materials with an expansion coefficient of 12×10 ^-6 m/( m·℃) of stainless steel; sealing with glass outer tube 1, glass inner tube 2 and corrugated expansion joint 3 respectively by fusion sealing connection and solder welding process; the vacuum degree of the vacuum space is 5×10 ^-5 Pa. All the other structural forms and parameters are the same as in Example 1.

The heat collecting tube in this embodiment is used in the compound parabolic concentrating system, the heat collecting efficiency of the heat collecting tube reaches 65% to 75%, and the heat collecting temperature range is 0 to 150°C; when the working temperature is 150°C, the thermal stress of the heat collecting tube is higher than that of the straight-through metal- The glass vacuum heat collector is reduced by about 50%.

Example 4

In yet another embodiment of the present invention, the length of the glass outer tube 1 is 4m; the wave number of the wave expansion joint is 3; the materials of the transition coupling ring I6 and transition coupling ring II7 have an expansion coefficient of 6×10 ^-6 m/(m·°C) Fe-Ni-Co Kovar alloy, the rest of the structure and parameters are the same as in Example 2.

The heat collecting tube in this embodiment is used in the trough-type concentrating system, the heat collecting efficiency is 75% to 85%, and the heat collecting temperature range is 0 to 300°C; when the working temperature is 300°C, the thermal stress of the heat collecting tube is higher than that of the straight-through metal-glass vacuum The heat collecting tube is reduced by about 80%.

Claims (7)

1. a warm straight through type all glass vacuum thermal-collecting tube in, is characterized in that being made up of outer glass tube (1), glass inner tube (2), the first corrugated-type expansion joint (3 (A)), the second corrugated-type expansion joint (3 (B)), the first metal connecting tube (9 (A)) and the second metal connecting tube (9 (B)); Be vacuum space (4) between outer glass tube (1) and glass inner tube (2), glass inner tube (2) outer surface is coated with the coating for selective absorption (8) of high-absorbility low-launch-rate; Getter (5) is posted near end position in glass inner tube (2) outer surface side; Outer glass tube (1) one end is by one end sealing-in of First Transition coupling ring (6 (A)) with the first corrugated-type expansion joint (3 (A)), and the other end is by one end sealing-in of the second transition coupling ring (6 (B)) with the second corrugated-type expansion joint (3 (B)); The other end of the first corrugated-type expansion joint (3 (A)) and the second corrugated-type expansion joint (3 (B)) is respectively by the two ends sealing-in with glass inner tube (2) of the 3rd transition coupling ring (7 (A)) and the 4th transition coupling ring (7 (B)); First metal connecting tube (9 (A)) and the second metal connecting tube (9 (B)) are welded in the outside mouth of pipe of the first corrugated-type expansion joint (3 (A)) and the second corrugated-type expansion joint (3 (B)) respectively.

2. middle temperature straight through type all glass vacuum thermal-collecting tube according to claim 1, is characterized in that the material of described outer glass tube (1) and glass inner tube (2) is Pyrex; Described glass inner tube (2) diameter range is 30 ~ 70mm, and length is 1 ~ 4m; Described outer glass tube (1) diameter 10 ~ 30mm larger than glass inner tube (2).

3. middle temperature straight through type all glass vacuum thermal-collecting tube according to claim 1, is characterized in that two described corrugated-type expansion joint materials are stainless steel; Waveform is U-shaped or Ω type, and wave-number range is 1 ~ 10.

4. middle temperature straight through type all glass vacuum thermal-collecting tube according to claim 1, is characterized in that four described transition coupling rings are stainless steel or expansion alloy; The coefficient of expansion of material is 3 × 10 ^-6~ 12 × 10 ^-6m/ (m DEG C).

5. middle temperature straight through type all glass vacuum thermal-collecting tube according to claim 1, is characterized in that the vacuum of described vacuum space (4) is 5 × 10 ^-5~ 0.05Pa.

6. middle temperature straight through type all glass vacuum thermal-collecting tube according to claim 1, it is characterized in that the absorptivity of described coating for selective absorption (8) is 86% ~ 96%, emissivity is 4% ~ 14%.

7. middle temperature straight through type all glass vacuum thermal-collecting tube according to claim 1, is characterized in that the sealing-in of two corrugated-type expansion joints and outer glass tube (1) and glass inner tube (2) connects form and is external or built-in.