JPS598737B2 - Vacuum solar collector - Google Patents

Description

[Detailed description of the invention] The present invention relates to a vacuum type solar heat collector.

Vacuum solar heat collectors, in which heat collecting plates, heat collecting metal tubes, etc. are housed in a glass container and the inside of the glass container is evacuated to a high degree of vacuum, have less heat loss through convection and conduction due to vacuum insulation, so they can withstand high temperatures. It is possible to collect heat and has high heat collection efficiency.

In this type of heat collector, the glass and metal must be sealed in order to enclose the heat collecting metal tube inside the glass container.

Since the degree of vacuum within the glass container affects the heat collection efficiency, this sealed portion must be able to withstand a high degree of vacuum.

It is also necessary to have high mechanical strength, thermal shock resistance, and heat resistance.

However, solar heat has a low energy density, so in order to increase the amount of heat collected, it is necessary to make the collector wider and the glass container also larger.

For example, in the case of glass tubes, those with an outer diameter of 80 to 100 mm and a length of 1,500 to 2,500 plates are used.

As described above, conventional heat collectors in which a metal is sealed to a glass tube having a large outer diameter and length have problems such as high manufacturing cost and difficulty in maintaining a high degree of vacuum for a long period of time.

The present invention provides a heat collector that solves these problems.

In the solar heat collector of the present invention, since the diameter of the portion of the glass container that is sealed to the metal is small, the metal that is sealed to the glass can be made small.

Glass has a lower thermal conductivity than metal, so making the metal part smaller reduces heat loss, and making the glass part larger allows for more light, improving the efficiency of the heat collector.

The diameter of the glass sealing fittings should be slightly larger (about 4 to 10 mm) than the outer diameter of the heat collecting metal tube, and the length should be as short as possible (15 to 25 holes) to seal the glass tube. It can be made extremely small.

Glass sealing fittings generally have poorer corrosion resistance than stainless steel and are more expensive.

The present invention solves these drawbacks by downsizing the glass sealing fitting.

Steel pipes are widely used as heat collecting metal pipes due to their corrosion resistance and thermal conductivity, but since it is difficult to bond the steel pipes and glass sealing fittings directly due to the process, we use intermediate fittings made of the same material as the heat collecting metal pipes. was used.

Since the expansion coefficient of the intermediate metal fitting is usually larger than that of the glass sealing metal fitting, the intermediate metal fitting was glued over the outer periphery of the glass sealing metal fitting to suppress the generation of thermal stress due to the difference in expansion coefficient.

By sealing the glass container and metal at only one point and minimizing the sealing area, the probability of internal vacuum leaking is greatly reduced, and reliability is improved accordingly.

Further, since the direct sealing between glass and metal is performed by high temperature heating, the metal diffuses into the glass, resulting in a strong seal.

Compared to sealing using frit glass for sealing with a low melting point, this not only has higher mechanical strength but also has better thermal properties such as thermal shock and heat cycle.

The present invention will be explained in detail with reference to embodiments shown in FIGS. 1 and 2.

A glass cap 2 having a small-diameter opening 3 is previously formed, and its end 2' is welded to the glass container 1.

The glass material of the glass cap 2 may be the same as that of the glass container 1 or any material that can be welded to the glass container 1 without any problem.

Alternatively, one end of the glass container 1 may be heated and softened and drawn into a shape having vacuum resistance strength as shown in the figure, or it may be blown into a drawn shape from the beginning.

On the other hand, a metal for glass sealing that can be well sealed with the glass container 1, for example, when the glass container 1 is soda lime glass (expansion coefficient is around 95X10-7/℃), 42%Ni is used.
6 S C r steel, borosilicate glass (expansion coefficient is 50
×10-7/°C), a heat collecting metal tube 8 is attached to one end of a cylindrical sealing fitting 6 (the diameter is approximately the same as the small diameter opening 3 of the glass container 1) made of Kovar alloy etc. Is it the same metal?
Alternatively, a metal intermediate fitting 7 with approximately the same coefficient of thermal expansion and excellent corrosion resistance is placed over the outer periphery of the glass sealing fitting 6 and bonded (
Welded or brazed), prepare this sealing metal fitting 6.
The other end 6' of is sealed to the opening 3.

Of course, the sealed and welded parts should be sufficiently strained.

Next, the heat collecting metal tube 8 to which the heat collecting plate 10 is attached is inserted into the glass container 1 from the end 1', and the end 8' of the metal tube 8 is made to protrude outside the relay fitting 7.

The other end is sealed.

The heat collecting metal tube 8 is made of a metal having good thermal conductivity and excellent corrosion resistance, such as copper.

The heat collecting metal pipe 8 and the relay fitting 7 are welded or brazed.

An elastic support 11 is attached near the sealed end of the heat collecting metal tube 8 and at a position necessary to support the heat collecting plate 10, and the metal tube 8 is supported at the center of the glass container 1.

An exhaust pipe 5 made of the same glass is welded to a separately formed glass cap 4 made of glass having the same composition as the glass container 1 or a glass material that can be welded to the glass container 1 without any problem. ' and end 1 of glass container 1
′ are welded together.

Thereafter, the air is exhausted from the exhaust pipe 5 and the exhaust pipe 5 is closed.

．． In this way, a solar heat collector utilizing the heat pipe principle as shown in FIG. 1 can be obtained.

A heat collector of a type that extracts solar heat using a heat collecting fluid as shown in FIG. 2 can be further obtained in the following manner.

The heat collecting inner tube 9 is inserted into the metal tube 8 from its end 8' until the end of the heat collecting inner tube 9 reaches near the sealed end of the metal tube 8, and held by suitable means.

The outer diameter of the heat collecting inner tube 9 is considerably smaller than the inner diameter of the metal tube 8.

The heat collecting inner tube 9 can be made of metal or glass with excellent corrosion resistance.

The heat collection fluid is injected from the end 9' of the heat collection inner tube 9 and flows out from the end 8' of the metal tube 8 to extract solar heat.

FIG. 3 shows another embodiment.

The glass sealing metal used in the solar heat collector of the present invention is:
Since it is sufficient to use only one extremely small piece, corrosion can be easily prevented.

Furthermore, since the metal part has a small surface area and is compact, heat dissipation from the metal part is extremely small.

Further, since the sealing portion between the glass tube and the metal is small, it is easy to seal the glass tube, it is easy to obtain good sealing, and the manufacturing cost is low.

Therefore, a highly reliable solar collector that can withstand high vacuum conditions and has high mechanical strength can be obtained.

[Brief explanation of drawings]

FIGS. 1, 2, and 3 are cross-sectional views showing embodiments of the present invention. 1: Glass container, 6: Sealing fitting, 7: Intermediate fitting, 8:
Heat collecting metal tube.

Claims (1)

[Claims] 1 In a vacuum type solar heat collector, one end of the metal cylindrical sealing fitting for glass sealing is directly sealed to the small-diameter opening of the glass container, and the other end is connected to the heat collecting metal tube. An intermediate fitting made of a metal with a thermal expansion coefficient that is the same as or similar to the expansion coefficient is placed over the outer periphery of the sealing fitting, and the heat collecting metal tube is inserted into the glass container, and the intermediate fitting and the heat collecting metal tube are connected. A vacuum type solar collector with a structure in which the