JPS6033218B2 - solar collector - Google Patents

Description

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

Although vacuum glass tube type solar collectors can heat the heat medium to high temperatures, they have various problems in terms of manufacturing and lifespan.

This point will be explained with reference to a conventional vacuum glass tube type 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 a selective absorption film on at least its outer surface, and is made by, for example, 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 steel pipe or the like. made by.

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 a seal plate at the end of the outer glass tube 1, which is made of iron, nickel, chromium alloy, etc. whose expansion coefficient is similar to that of glass in order to be firmly fixed to the outer glass tube 1. For example, they are fused using a sealing material such as a 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 chip tube is sealed. 8 is a cylindrical heat collector 2
This is a spacer for holding the glass tube in 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 seal plate 6, and the fused portion is likely to partially break. 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 or the like is used for the hard secondary glass, and low melting point glasses with matching expansion coefficients are used as the sealing material. Now, generally, the above-mentioned configuration is used to prevent damage to the collector that is repeatedly heated and cooled, but the inventors of the present invention have found that there are phenomena that cannot be adequately addressed with this configuration. I put it out.

It is caused by the heat collector 2 as a transient phenomenon during heating or cooling.
This is a phenomenon in which a temperature difference occurs between the outgoing pipe section 4 to which nothing is fixed and the return pipe section 5 to which nothing is fixed. This temperature difference causes a difference in length in all axial directions of the two pipe parts 4 and 5, resulting in a fused part of the seal plate 6, a joint part 9 and 10 of the seal plate 6 and the heat collecting pipe 3, or a U Stress that causes damage acts on the character-shaped bent portion 3a, causing the joints 9 and 10 to come off and the seal plate 6 to crack, causing slow leaks (vacuum leaks).
Moreover, buckling as shown in FIG. 3 occurs in the U-shaped bent portion 3a, causing inconvenience in the circulation of the heat medium. The above phenomena are thought to occur in all of the following cases where the collector temperature changes. [During normal operation of the collector]
If the heat collecting plate 2, heat collecting pipe 3, etc. approach the outside temperature after the circulation of the heat medium stops near sunset,
Until the onset of solar radiation (follows changes in outside temperature).

[During abnormal operation]

8. When the heating medium is not circulated during the day and night, and the heating is done in an empty state.

In this case, it is heated and cooled within a range of about 20,000 degrees normal temperature throughout the day, but as with normal operation, the temperature changes drastically at sunrise and sunset. 'vs. When the heating medium is suddenly circulated during dry cooking during the day.

Temperature changes are large because a low-temperature heat medium is suddenly sent into a heat collection pipe of about 200 qo.

[During the manufacturing process]

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.

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. Figures 4, 5, and 6 are cross-sectional views of the solar collector of the present invention.
The same parts as in Figure 2 are designated by the same symbols. 4, 5, and 6 are characterized by two independent cylindrical heat collectors 11,
12 are arranged side by side in the outer glass tube 1 with a slight gap, the heat collector 11 is fixed to the forward tube section 4, and the heat collector 12 is fixed to the return tube section 5. In other words, the feature is that the thermal conditions in the exchange parts 4 and 5 are made the same by providing cylindrical heat collectors separately for both exchange parts 4 and 5. The heat collectors 11 and 12 have the same shape and size, are coated with a selective absorption film on at least their outer surfaces, and are made by extrusion of aluminum.

Further, the heat collector 11 has a cylindrical holding hole 1 formed on the inner peripheral surface.
1a is tightly fixed to the outgoing pipe section 4 in a heat conductive manner, and the other heat collector 12 is fixed to the cylindrical holding hole 1 similarly formed on the inner circumferential surface.
2a is closely fixed to the return pipe portion 5 in a heat conductive manner. Therefore, the fixing section 1 of the heat collector 11 in the forward inspection section 4
, and the fixed portion 12 of the heat collector 12 in the return pipe section 5 are the same, and the conditions during heating and cooling in both the pipe sections 4 and 5 are almost the same. Incidentally, in fixing the heat collectors 11 and 12, a mechanical crimping method is adopted in which the heat collecting pipe 3 of the same machine is expanded as shown in FIG. 13,13...
is a spacer for holding the heat collectors 11 and 12 at predetermined positions in the outer glass tube 1.

According to the collector configured as described above, since the heating and cooling conditions of both the pipe sections 4 and 5 are almost the same, the heating and cooling of both the pipe sections 4 and 5 can be repeated with almost no temperature difference. It will be. Therefore, the exchange parts 4 and 5 have no difference in thermal expansion,
Since thermal expansion and contraction are repeated evenly starting from the seal plate 6, the above-mentioned disadvantageous force due to the difference in thermal expansion does not occur. Therefore, reliability against slow leaks and buckling is improved, and high performance can be maintained for a long period of time. or,
With such a configuration, when installing a solar heat collection system, connection and piping can be performed without distinguishing between the outgoing pipe 4 and the returning pipe 5 in the heat collecting pipe 3, which brings about a great advantage in terms of construction. [Other Examples] {1' The above example was a case in which a plurality of heat collectors of the same shape and size were arranged side by side. The total fixed length of the portion 4 and the total fixed length of the return pipe 5 may be made to be the same.

■ An even number of heat collectors of the same shape and size may be arranged in parallel and alternately fixed to the forward detector 4 and the return detector 5.

In this way, the thermal conditions of the exchange units 4 and 5 will be more similar. {3} In the above embodiments, a plurality of heat collectors are installed in parallel, but one heat collector 2 is fixed to both the forward pipe section 4 and the return pipe section 5 with the same length. It is also possible that you did.

In this case, since the thermal conditions of both the tube parts 4 and 5 are substantially the same, no unfavorable force is generated due to the difference in thermal expansion between the exchange parts 4 and 5.

However, this time, the following phenomenon becomes a problem. This is a phenomenon in which the heat collector 2 mechanically bonded to the heat collecting pipe moves to the right or left on the pipe 3 due to repeated heating and cooling.

It is not clear why this phenomenon occurs, but it is thought to be because the heat collecting plate 2 is made of aluminum N and the heat collecting pipe is made of copper Cu, and the coefficients of thermal expansion of the two are different. When this phenomenon occurs, for example, in a collector as shown in FIG. 10 or seal plate 6
There is a risk that the heat collecting pipe itself may be damaged, and on the other hand, if it moves to the left, the U-shaped bent portion 3a of the heat collecting pipe 3 may be pressed against the end of the heat collecting plate 2 and deformed, so in this case, This is prevented by welding detents to the outgoing pipe portions 4 on the outside of both ends of the heat collector 2. Since the detent is directly welded to the outgoing pipe section 4, it will not move due to heating or cooling. On the other hand, when one heat collector is fixed to both pipe parts 4 and 5, the heat collector part fixed to the outgoing pipe part 4 and the heat collector part fixed to the return pipe part 5 are reversed. Sometimes there is a force that tries to move in the direction.

That is, if the forward pipe section 4 side is in the direction of the seal plate 6, the return pipe section side is in the direction of the bending section 3a. In such a case, it is not very useful to provide detents on the outside of both ends of the heat exchanger, and the direction in which the heat collector straddles the exchange parts 4 and 5 is used to bring them closer together is not very helpful. This will cause the pipe portions 4 and 5 to bend or buckle. Therefore, it is extremely inconvenient to fix one heat collector to either of the tube sections 4, 5. In the case of the embodiment shown in FIG. 4, if a movement phenomenon occurs in the heat collectors 11 and 12, this phenomenon can be prevented by providing movement stops for each.

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

Moreover, this collector has a great advantage in terms of installation work, since it is not necessary to distinguish between an outgoing pipe section and a return pipe section.
Brief description of the drawings Figure 1: A sectional view of a conventional solar collector, Figure 2: A sectional view of the main part of Figure 1, Figure 3: An explanatory diagram of the buckling phenomenon, Figure 4: A solar collector of the present invention. Fig. 5: A-A' sectional view, Fig. 6: B-B' of Fig. 4.
Cross-sectional view.

Code, 3: Heat collection pipe, 4: Outgoing pipe section, 5: Warped pipe section,
11, 12: Heat collector.

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1 In a solar heat collector consisting of a U-shaped heat collecting pipe enclosed in a transparent container and heat collecting fins fixed to the heat collecting pipe, the heat collecting fins are fixed to the outgoing pipe section and the heat collecting fins are fixed to the return pipe section. A solar heat collector characterized in that a plurality of heat collecting fins are arranged in parallel, and the fixed portions of the heat collecting fins in the outgoing pipe section and the return pipe section are approximately the same length.