JPS5952739B2 - Solar heat collector tube and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solar heat collecting tube, particularly a solar heat collecting tube in which a heat collecting plate, a heat collecting metal pipe, etc. are housed in a glass tube and the inside of the glass tube is evacuated, and a method for manufacturing the same.

Solar heat collection tubes are made by evacuating the inside of the glass tube to a high degree of vacuum to prevent heat loss due to air convection and conduction.

If this vacuum leaks, the heat collection effect will be significantly reduced, so vacuum leaks must not occur even during long-term use.

Therefore, solar heat collecting pipes must (1) have thermal shock resistance that will not cause cracks or damage due to heating and cooling during the exhaust process during manufacturing, or from rapid cooling during mountain opening after receiving strong solar heat in the summer; .

(2) It must have mechanical strength that will not be damaged by external forces applied during assembly work that connects a large number of heat collecting metal pipes to each other, or by forces caused by expansion and contraction due to heat during use.

(3) High vacuum degree must be maintained reliably. (4) It must have chemical durability that will not cause deterioration or alteration of the material even if it is exposed to outdoor natural conditions for a long period of time.

etc. are required. In particular, sufficient consideration must be given to these points in the sealing part between the glass tube and metal and in the processing part of the glass tube.

On the other hand, as a method for sealing metal and glass tube, (1)
The method must be suitable for mass production.

(2) The method is such that the heat collecting plate and heat collecting metal pipe housed inside the glass tube are not heated to high temperatures during the manufacturing process.

(3) It must be a method with low manufacturing cost. etc. are required.

Conventional solar heat collection tubes have a structure in which the heat collection plate and heat collection metal pipe are housed in a glass tube, and then the glass tube and metal stem are sealed at both ends of the glass tube. At times, the heat collecting plate and heat collecting metal pipe housed in the glass tube are exposed to extremely high temperatures, which causes the selective absorption film provided on the surface of the heat collecting plate to deteriorate and the heat collecting metal pipe to oxidize. This caused a decrease in heat collection effectiveness and poor exhaust.

In addition, due to distortion occurring at the sealing portions with the metal stem at both ends of the glass tube, thermal shock resistance and mechanical strength were reduced.

If strain is completely removed, thermal shock resistance and mechanical strength will improve, but in order to completely remove strain, for example, borosilicate glass must be heated to 570°C or higher, soda lime glass to 500°C or higher. It is necessary to heat it once and then cool it down.

However, this heating deteriorates or oxidizes the heat collecting plate and the heat collecting metal pipe, causing the above-mentioned defects, making it virtually impossible to completely remove the strain.

In conventional solar collector tubes, the degree of processing at both ends of the glass tube during sealing was large, leaving considerable distortion.

The present invention provides a solar heat collector tube in which no strain remains at one end of the glass tube, deterioration of the heat collector plate, and oxidation of the heat collector metal pipe, and a method for manufacturing the same.

Embodiments of the present invention will be described in detail below with reference to the drawings.

The glass stems 2 and 2' are made in advance from borosilicate glass having the same composition as the glass tube 1°.

The diameter of the glass stems 2, 2' is approximately the same as the outer diameter of the glass tube 1°, and there are holes 3, 2' in the center through which the heat collecting metal pipe 10 is passed.
3' is provided.

The diameters of the holes 3, 3' are made slightly larger than the outer diameter of the heat collecting metal pipe 10, and the peripheral portions of the holes 3.3' have a shape suitable for sealing the connecting fitting 4.

One of the glass stems 2' is further provided with a small hole 5, and an exhaust pipe 6 for evacuating the inside of the glass tube 1° is sealed.

The connecting fitting 4 is made of a metal having an expansion coefficient close to that of the annular glass, such as a cover metal, and the end to be sealed to the glass stems 2, 2' has a diameter larger than the holes 3, 3' of the glass stem. The tip is tapered in the shape of a knife edge to obtain a favorable seal.

The diameter of the other end is smaller, and its inner diameter is just large enough to allow the heat collecting metal pipe 10 to be inserted therein.

Connecting fittings 4 are sealed to the glass stems 2, 2', respectively.

The sealing method used was a known method such as press-fitting the connecting fitting 4 into glass while heating it with a high-frequency coil.

Glass stem 2 with connecting fitting 4 or exhaust pipe 6 sealed
, 2' completely remove the strain through the strain removal process.

The connecting fitting 4 and the exhaust pipe 6 are sealed, and the completely strain-free glass stem 2' is sealed to one end 1' of the glass tube 1° using a gasper or the like.

Immediately thereafter, the strain is completely removed in a strain removal process.

A heat collecting metal pipe 10 with a heat collecting plate 11 attached thereto is inserted from the other end 1 of this glass tube 1o, and the opposite end 1'
A heat collecting metal pipe 10 is made to protrude outward from a connecting fitting 4 of a glass stem 2' which is sealed to the glass stem 2'.

A glass stem 2 is brought into contact with an end 1 of a glass tube 1°, and a heat collecting metal pipe 10 is passed through its connecting fitting 4.

Next, the heat collecting metal pipe 10 and the heat collecting plate 11 are pressed toward the glass tube end]' so that the heat collecting plate 11 is at the farthest position from the end 1 of the glass tube 1°, The end 1 of the glass tube 1° and the glass stem 2 are sealed.

For sealing, the distance between the glass tube 1o and the glass stem 2 should be made as small as possible so that they are in close contact with each other, and the flame should be as thin as possible and the direction of the flame should not be directed toward the center of the glass tube 1°. Direct the heat collecting metal pipe 10 in the circumferential direction as much as possible, using a flame electrode, etc. to prevent the heat collecting metal pipe 10 from being exposed to high-temperature flames.

After sealing, gradually cool while heating with flame to avoid distortion as much as possible.

After cooling down sufficiently, push the heat collecting metal pipe 10 and remove the heat collecting plate 1.
1 is returned to the center of the glass tube 1°, and the contact portions between the connecting fittings 4 of the glass stems 2 and 2' and the heat collecting metal pipe 10 are welded to prevent vacuum leakage.

The length of the connecting fitting 4 is set to such a length that the high temperature of the welded portion is not transmitted to the sealed portion between the connecting fitting 4 and the glass stems 2, 2'.

Next, after exhausting the air from the exhaust pipe 6, the exhaust pipe 6 is closed to complete the process.

Heat collecting metal pipe 1 due to temperature change during use of solar heat collecting pipe
The expansion and contraction of 0 is absorbed by the diaphragm 12 and the like.

The heat collecting plate 11 is held approximately at the center of the glass tube 1° by a center holder 13.

In order to make the solar heat collector tube according to the present invention smaller than the sealed part between the glass stem 2 and the glass tube end 1, the glass material is pongee silicate glass (expansion coefficient 30~55X 10-7/'C).
) is preferable.

In addition, in the case of using borosilicate glass, the part of the connecting fitting 4 that is sealed to the glass is made of cover metal, and the part that is welded to the heat collecting metal pipe 10 is made of the same metal as the heat collecting metal pipe 10, such as copper, It may also be made of other metals and welded together.

In the embodiment, the exhaust pipe 6 is a thin glass tube sealed to the glass stem 2', but it may also be sealed to a glass tube 1°, or a thin copper tube may be welded to the connecting fitting. May be used.

The solar heat collection tube according to the present invention has almost no deterioration of the heat collection plate during the manufacturing process, has good heat collection efficiency, can withstand long-term use, has low manufacturing cost, and is suitable for mass production.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view showing an embodiment of the present invention. 1o; glass tube; 2, 2'; glass stem; 4; connection fitting; 10; heat collecting metal pipe; 11; heat collecting plate.

Claims (1)

[Claims] 1. A glass stem is sealed at both ends of the glass tube, and a hole larger than the outer diameter of the heat collecting metal pipe is provided in the center of the glass stem, and the area around this hole is It has a tubular fitting that is sealed to the glass tube, and this fitting protrudes toward the outside of the glass tube, and its tip gradually becomes thinner, and its inner diameter is approximately equal to the outer diameter of the heat collecting metal pipe. The heat collecting metal pipe protrudes outside the glass tube through this connecting fitting, and the contact area between the heat collecting metal pipe and the connecting fitting is hermetically welded, and the heat collecting plate is housed inside the glass tube. Solar heat collection tubes are evacuated to a high degree of vacuum. 2. A step of preparing a glass stem having a hole in the center that is larger than the outer diameter of the heat collecting metal pipe and sealing one end of a tubular connecting fitting around the hole; The process of removing distortion in the glass tube with the glass stem sealed is the process of inserting a heat collecting metal pipe with a heat collecting plate attached from the other end of the glass tube, pushing it as far as possible towards the stem side, and from the same side. Pushing another glass stem through the heat collection metal pipe into its connection fitting and sealing this glass stem to the glass tube, then pulling back the heat collection metal pipe and forcing the heat collection plate into the center of the glass tube. A method for manufacturing a solar heat collector tube, which comprises the steps of airtight welding the heat collecting metal pipe and the connecting fittings after the heat collecting metal pipe is placed in the section, and a step of evacuating the inside of the glass tube to achieve a high degree of vacuum.