JPS6033217B2 - solar collector - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in solar heat collectors.

Although vacuum glass tube type solar collectors can raise the temperature of the external heating medium to high temperatures, there are various problems in terms of manufacturing and lifespan.

This point will be explained with reference to a conventional vacuum glass tube solar collector shown in FIGS. 1 and 2.

First, in FIGS. 1 and 2, 1 is an outer glass tube that serves as a transparent cover and a box. Reference numeral 2 denotes a cylindrical heat collector having at least an outer surface coated with a selective absorption film, and is made, for example, by aluminum extrusion molding.

3 is a heat collection pipe that thermally adheres to the cylindrical heat collector 2 and serves as a passage for a heat medium heated by obtaining heat from the cylindrical heat collector 2 heated by solar heat, and is made of a steel pipe or the like. Made.

This heat collecting pipe 3 is made by bending a single pipe into a U-shape.
An outgoing pipe part 4 and a return pipe part 5 are formed, and after the outgoing pipe part 4 is inserted into a cylindrical insertion hole 2a formed inside the cylindrical heat collector 2, it is internally fixed by expansion. Reference numeral 6 denotes an end seal plate of the outer glass tube 1, which is made of iron, nickel, etc. whose expansion coefficient is similar to that of glass in order to secure it to the outer glass tube 1.
It is made of a chromium alloy or the like, and is fused to the outer glass tube 1 using a sealing material such as low melting point glass frit.

Moreover, the heat collecting pipe 3 is brazed. In this way, the outer glass tube 1 and the seal plate 6 form a vacuum container. 7 is a space surrounded by the outer glass tube 1 and the seal plate 6, and is a chip tube (not shown).

) is evacuated by a vacuum pump and the vacuum section is created by sealing the chit tube. Reference numeral 8 denotes a spacer for holding the cylindrical heat collector 2 at a predetermined position inside the outer glass tube 1, and is made of, for example, ceramic.

Such a collector has the disadvantage that the force generated by the thermal expansion of the heat collecting pipe 3 is applied to the sealing plate 6, and the fused portion tends to be partially destroyed. Therefore, when sealing the glass tube 1, it is necessary to make the sealed part strong by matching the thermal expansion coefficients of the glass tube 1, the sealing plate 6, and the sealing material. Kovar and the like are used for alloys and hard secondary glasses, and low melting point glasses with matching expansion coefficients are used as sealing materials.
Now, generally, the above-mentioned configuration is used to prevent damage to the collector due to repeated heating and cooling, but the inventors of the present invention have found that there are phenomena that cannot be adequately dealt with with such a configuration. I put it out.

■ One of them is that the outgoing pipe section 4 is repeatedly heated and cooled.
This is a phenomenon in which the heat collector 2 mechanically bonded to the body moves to the right or left over the body 4. It is not clear why this phenomenon occurs, but it is thought to be because the heat collector 2 is made of aluminum AI, the heat collecting pipe is made of U, and the coefficients of thermal expansion of the two are different. When this phenomenon occurs, for example, when the heat collector 2 moves to the right in FIG. Alternatively, the seal plate 6 itself may be damaged. On the other hand, when moving to the left, there is a risk that the U-shaped bent portion 3a of the heat collecting pipe 3 will be pressed against the heat collecting body 2 and deformed. (2) The other phenomenon is a transient phenomenon during heating or cooling, in which a temperature difference occurs between the outgoing pipe section 4 to which the heat collector 2 is fixed and the return pipe section 5 to which nothing is fixed.

This temperature difference causes a difference in the lengths of the exchange parts 4 and 5 in the vertical direction, and as a result, stress that causes damage to the joint parts 9 and 10 or the U-shaped bent part 3a acts on the joint parts 9 and 10, and 10 may come off or the seal plate 6 may crack, causing a slow leak (vacuum leak), or the U-shaped bent portion 3a may buckle as shown in FIG. cause inconvenience.
The phenomenon (2) above is thought to occur in the following cases when the temperature of the collector changes.

[During normal operation of the collector] From the time when solar radiation begins until the heating medium circulates, the heating medium is circulating, but if the amount of solar radiation or outside temperature changes When the heat collector 2, heat collection pipe 3, etc. approach the outside temperature after the circulation of the medium stops P} After W until the start of solar radiation (follows the change in outside temperature) [During abnormal operation] { When the heating medium is not circulated during the day and night and the air is blown dry.

In this case, about 200 qo is heated and cooled throughout the day within a room temperature range, but as with normal operation, the temperature changes drastically at sunrise and sunset.

H: When the heating medium is suddenly circulated during the day when the heating medium is dry-cooked.

Since a low-temperature heat medium is suddenly sent into the heat collection pipe of about 200 oo, the temperature changes are large.

[During the manufacturing process]

Kawa: For example, because it is heated to several hundred degrees during vacuum extraction, it undergoes heating and cooling changes from room temperature to several hundred degrees to room temperature.

On the other hand, the above phenomenon (■) occurs except in the case of 'o} where there is almost no temperature difference between the outgoing pipe part 4 and the return pipe part 5 due to the circulation of the heat medium among the above mentioned rivers. Conceivable.

The present inventors observed the above-mentioned phenomenon based on various experiments,
At the same time, by adding research ingenuity, we succeeded in preventing this phenomenon with an extremely simple configuration.

The solution will be explained below with reference to the drawings. 4th, 5th
The figure is a sectional view of the solar collector of the present invention, and the same parts as in FIGS. 1 and 2 are designated by the same reference numerals. In FIG. 4, reference numeral 11 denotes a connector provided to prevent the above-mentioned phenomenon, and bridges and maintains the outgoing pipe section 4 and the return pipe section 5 on the outside of both ends of the heat collector 2. This connector 11 is made by bending a single metal bar into the shape of a pair of glasses as shown in FIG. Afterwards, they are fixed to the inspectors 4 and 5 by brazing or welding, respectively. In this way, the connector 11 that is welded or brazed to the heat collecting pipe 2 will not be displaced due to heating or cooling unlike the heat collecting body 2, even if the material is different from that of the pipe 3.

According to the above configuration, thermal strain based on the temperature difference between the forward inspector 4 and the return inspector 5 mainly occurs between the two connected odors 11, 11,
The force acting between the tubes 4 and 5 due to the temperature difference is reduced at the connecting member 11 and no longer acts directly on the joints 9 and 10 and the U-shaped bent portion 3a.

Therefore, cracks in the seal plate 6 and buckling of the bent portion 3a can be prevented. Note that even if there is only one connected odor 11, the side where it is provided is protected, so two of them are not necessarily required.

Furthermore, since the movement of the heat collector 2 is stopped at the portion where the connector 11 is provided, damage caused by the phenomenon (2) above can be prevented.

As described above, according to the present invention, it is possible to provide a collector that has durability against repeated heating and cooling.

[Brief explanation of drawings]

Figure 1: Cross section of secondary solar collector, Figure 2: 1st
A sectional view of the main part of the figure, Figure 3: An explanatory diagram of the buckling phenomenon, Figure 4:
Cross-sectional view of the solar collector of the present invention, FIG. 5: its A-A
'Cross-sectional view, Figure 6: Plan view of the connector. Code, 3: Heat collection pipe, 4: Outgoing pipe section, 5: Return inspector,
11: Connector. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. In a solar heat collector comprising a U-shaped heat collecting pipe enclosed in a transparent container and a heat collecting fin fixed to the heat collecting pipe, in a portion of the heat collecting pipe other than the part to which the heat collecting fin is fixed, A solar heat collector characterized in that an outgoing pipe section and a return pipe section of the heat collecting pipe are bridged by a connector.