JPS6093252A - Solar heat collector - Google Patents

Abstract

PURPOSE:To improve the weatherproof property of sealing and welding part and make it employable for a long period of time by a method wherein the layer of glass powder, same as the glass outer tube in the material thereof, is adhered previously to a part whereat the outer tube of glass is welded to a metal for welding and thereafter the powder is heated to weld. CONSTITUTION:The part whereat the outer tube 1 of soda glass is welded to the metallic member for sealing and welding is interposed previously with a layer 9 of the fine powder (1-500m) of soda glass whereby the layer 9 of fine powder of same material as the glass outer tube 1 is molten easily and become flowable sufficiently and both of the members are welded rigidly by a good mutual diffusion between both materials of the metal 6 and the outer glass tube 1. Further, generation of too thick oxide film on the surface due to the excessive heating of the metal may be prevented by the existence of the glass powder layer 9. As a result, the phenomena of separation between the internal metal and the oxide film of metal may be prevented and the reliability of the collector may be improved remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a solar collector in which a heat pipe is vacuum-sealed within a glass outer tube, and the reliability of the sealed portion between glass and metal is improved.

[Background of the invention]

Many types of solar collectors have already been developed, and the popular type is one in which a heat pipe with a heat transfer medium sealed inside a copper pipe is vacuum sealed in a glass outer tube that transmits heat rays well together with a heat collecting plate. The ratio seems to be relatively good.

Figure 1 shows an example of a conventional solar collector of this kind. 1 is a glass outer tube, 2 is a solar heat collector plate made of thin stainless steel or the like and coated with a reflective film of silver or aluminum on the surface, and 3 is a solar collector plate inside the glass outer tube. 1 - Support for maintaining proper relative position of pipes, solar heat collecting plates, etc., 4 is a heat pipe, 5 is a heat exchanger, 6 is a metal member for funnel-shaped sealing, 7 is an exhaust tip-off for the glass outer tube Section 8 is a welding point between the sealing metal member and the heat pipe. As mentioned above, the heat pipe is made of copper, but the coefficient of thermal expansion of copper is extremely large, about 7. A sealing metal member 6 is interposed between the heat pipes and a heat ray absorbing film is provided on the outer surface of the heat pipe.

The material of the metal member 6 for sealing is Fe-Ni or R, which can be optimally sealed to so-called soft glasses such as soda glass and lead glass.
'e-Ni-Cr alloy is used.

After these internal members are assembled into an integral structure and inserted into the glass outer tube, the glass outer tube 1 and the sealing metal member 6 are sealed and joined together at the section A in FIG. In addition, at the other end of the glass outer tube 1, the Q portion is pre-baked and rolled, an exhaust pipe is connected to the “C”, an integrated pickle is inserted and attached to the inside, and after hermetically sealing at the A portion, the inside is evacuated through the exhaust pipe. After exhausting the air, the exhaust tip-off section 7 performs tip-off.

The length of the glass outer tube is generally 2, 5 to 3 mm, in order to absorb as much heat as possible for solar heat collectors of this kind, in order to improve thermal efficiency. There are also about Osn, and a set of multiple pieces is used as 'ζ. Therefore, the amount of glass outer tubes used is enormous, and it is necessary to use glass materials that are as inexpensive as possible.

- Since these collectors are installed outdoors, they are exposed to moisture, wind and rain for a long time. Sun again! ; The grade is increased to 300°C by c. fj (=glass outer tube and L=1 fitting part), it't+?m will be exposed to high humidity and thermal fluctuations of temperature and temperature for a long period of time.

However, is the interface between metal and glass in the sealed part generally moisture-resistant, water-resistant, and heat-resistant? ij? Poor A properties, mechanical strength, adhesive properties, etc. The reason for this weakness is that the glass and metal are not sufficiently interdiffused and thermal fusion is not complete.

[Object of the Invention] An object of the present invention is to provide a solar collector that can be used for a long period of time and has improved weather resistance in the sealed portion between glass and metal.

[Summary of the invention]

In order to achieve the above object, in the present invention, soda glass, that is, 5i0260 to 75% by weight, is added to the glass outer tube.
Using a metal whose main components are 10 to 20% Na2O and 3 to IO% CaO, the part of the sealing metal to be sealed with the glass outer tube is preliminarily coated with the same 4A quality as the glass outer tube with a particle size of 1.
A layer of glass powder in the range of ~500 μIn was deposited and heated from °ζ.

Soda glass used for the outer tube has the lowest material cost and is easily available. The main components are as described above, and subcomponents such as MgO, K2O, Fe2O3, etc. may also be included. It is of M' quality, which is almost the same as the glass that is generally commercially available as window glass or plate glass.

5. By using this soda glass. Although the material cost is very low, when it is sealed with metal, the viscosity of the glass material shown in Figure 2 (shown as the common logarithm of the value expressed in voids)
As shown in the temperature characteristic diagram, soda glass has a relatively high viscosity compared to expensive lead glass. Adhesive strength is weakened due to insufficient heat build-up with metal. That is, when trying to heat and bond the outer 1 fU of soda glass to the metal member for sealing as it is, we also added
The adhesive strength becomes weaker due to sufficient mutual diffusion between the metal and the glass.

The present invention attempts to overcome the above-mentioned drawbacks by interposing in advance a layer of fine soda glass powder (1 to 500 .mu.m.) in the area where soda glass and metal are bonded. In other words, the fine powder layer, which is made of the same material as the glass outer tube, is easily melted due to its heat capacity, has sufficient fluidity, and is well interdiffused with the materials of both the metal and glass outer tube. It is firmly adhered. Here, the particle size of powder glass is 1~500μIT
The reason why it is limited to + is that if powder of 1 μm or less is used,
In addition, when using powder with a diameter of 500 μm or more, the capacity of the powder may not be sufficiently small and the desired value may not be obtained during heating/melting. 1 activity (/!L mobility), mutual diffusivity is 1η and 7
It's so hot.

Yet another advantage of the intervening glass dust layer is that it serves to prevent the metal from heating too much and forming too thick an oxide layer on the surface.

Namely 1. When the metal is heated excessively, the thickness of the oxide film on the surface becomes too large, and the stress due to the difference in coefficient of thermal expansion of the internal metal exceeds the allowable value, causing a problem between the internal metal and the metal oxide film. A peeling phenomenon occurs. By interposing a glass powder layer, such peeling phenomenon can be prevented from occurring. According to the present invention, it is possible to perform optimal sealing without causing distortion in the sealed portion.

[Embodiment of 5C light] Fig. 3 shows an enlarged sectional view of the sealed portion between the glass outer tube l and the sealing metal member 6 in an embodiment of the present invention, and 9 in the figure is the same as the glass outer tube. This is the part where high quality powdered glass is heated and melted and then solidified.

One end of the outer n of the soda glass with a length of about 3,000mm is left open, and the llh end is squeezed as shown in part Q in Figure 1. Connect the air trapping pipe and set it aside.Assemble the heat exchanger 5, P1 pipe 4, solar heat collection/limit 2, etc. at the predetermined positions.Meanwhile, F
Degrease and acetate the metal parts for sealing made of <・- to i- to r Dame 42 alloy), and remove the same material as the glass outer tube (quality 1-・500 /, 1 r++ Heat-seal the glass powder to make an airtight seal.Then, in the first step (not shown in step 1), heat the heat bath 42 (all bent parts for sealing) at the melting point 8. (Weld 1.) Insert the sliding part from one end of the glass pipe 1 and 7. Apply 1×vsv+rr plus]2 to a heating means such as ?.After that, vacuum exhaust from the exhaust port (1×01' Torr
, τ exhaust chin 11 part 7 off the chi knob and the sun is t
Lecta was completed.

The strength of the sealed portion of the solar collector made in this way was compared with that of the sealed portion of a solar collector in which the outer tube of soda glass was directly sealed to the metal member for sealing without using the glass powder. This comparative test tested heat pipes between 270 and 28
After heating the part A to 0°C and repeating dropping and stopping cold water (approximately 20°C) for 15 minutes in cycle mode, we examined glass cracks and adhesive peeling at the sealing part. After 500 cycles for all 10 samples, no abnormality was observed (7), whereas in the sample directly sealed without using a powder glass fused layer, 30 cycles increased by 1 to 2/150 cycles, and 3. Since peeling due to cracks in the glass bonded portion was observed in the sample No. 10, the test was discontinued.

〔Effect of the invention〕

As explained above, according to the present invention, the reliability of the sealed portion between the glass outer tube made of soda glass and the sealing metal member is significantly improved, and a solar collector that can be used for a long period of time is obtained.

[Brief explanation of the drawings] Figure 1 shows a heat pipe placed inside a glass outer tube in a vacuum-tight manner.
A side sectional view of a stopped solar collector, Fig. 2, 4, a viscosity-temperature characteristic diagram of [Fig. Seal with!
'+1; is an enlarged cross-sectional view. 1-Gas external shield, 2-heat collecting plate, 3-support 4-heat pipe, 6-metal part for sealing (A, Part 7.

Claims (1)

[Claims] In order to vacuum-tightly connect the heat pipe and the glass envelope, which have significantly different coefficients of thermal expansion, in a solar collector that has a structure in which the heat pipe and the heat collecting plate are vacuum sealed in a transparent glass envelope. In the part of the member made of sealing metal interposed between the two that is to be sealed with the glass envelope,
The particle size is l ~ 500μ in advance with the same material as the glass envelope.
1. A solar collector characterized in that a layer of glass powder in the range of m is applied and then sealed by heating.