JPS6242224B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum tube type heat collector, and more particularly to a solar heat collector equipped with a structure for preventing displacement of heat collecting plates.

A vacuum tube type heat collector is equipped with a light-transmissive outer tube and an inner tube as a heat transfer tube, and the space between the inner and outer tubes is kept in a vacuum state. Usually, a heat collecting plate with a selective absorption film formed on the surface is thermally connected to the heat transfer pipe in order to expand its heat collection area.The heat transfer pipe is made of copper and the heat collection plate is made of aluminum. Also, the outer tube is generally made of glass.

The reason why copper is especially used for heat transfer pipes is that copper has corrosion resistance,
This is because copper is excellent in durability, and is the most suitable material for heat transfer pipes that are prone to corrosion due to heat transfer and deterioration over time.

Further, since copper has good thermal conductivity, it is desirable that the heat collecting plate is also made of copper and is integrally constructed with the heat medium pipe, but since copper is relatively expensive, it is disadvantageous in terms of cost. Therefore, aluminum is usually used for the heat collecting plate, which is thermally connected with the heat medium pipe inserted therein, and constitutes the heat collecting part of the heat collector.

However, due to the difference in materials between the heat transfer pipes and the heat collection plate, the fitting between the heat transfer pipes and the heat collection plate becomes loose due to their relative thermal expansion difference, and the heat collection plate becomes the heat transfer plate. There was a problem in that the rotation of the heat collecting plate from the tube and the temperature gradient of the heat collecting plate itself caused differences in the rate of expansion, causing the position of the heat collecting plate to deviate widely from its original position in the heat transfer pipe.

For this reason, conventionally, the above-mentioned problem has been dealt with by fixing a part of the heat collecting plate to the heat medium pipe via a contact plate. Figures 1 and 2 show a vacuum tube type heat collector equipped with a conventional anti-slip structure. Figures A, B, and C represent an enlarged plan view, side view, and axial sectional view of the anti-slip structure, respectively. Reference numeral 1 denotes a light-transmitting outer tube, and a heat medium tube 2 is housed inside. Two heat collecting plates 3 are fitted to this heat medium pipe 2 at a predetermined interval, and the opposite ends of both heat collecting plates are made of the same material as the heat medium pipe 2. A contact plate 4 made of a certain copper or copper alloy is attached by rivets 5 or caulking, and the contact plate 4 and heat transfer pipe 2 are further joined by brazing 6 or welding. Since the heat collecting plate 3 is fixed to the heat medium pipe 2 via the contact plate 4, the problem of the heat collecting plate 3 rotating relative to the heat medium pipe 2 or causing a large deviation as in the conventional case is eliminated. It was resolved.

However, according to this configuration, since the two heat collecting plates 3 are connected by one contact plate 4, the stress caused by thermal expansion and contraction of the heat medium pipe 2 to the heat collecting plate 3 is applied to each heat collecting plate 3. With the end of the heat plate 3 where the contact plate 4 is not attached as zero, the heat collectors act in opposite directions from both heat collector plates with the contact plate as a border so that the contact plate that connects both heat collector plates is at its maximum. . For this reason, all the force generated in the contact plate is concentrated on the rivet 5 or the caulked portion that fixes the contact plate 4 and the heat collecting plate 3, and a problem arises in that large shear stress is applied there. This problem is particularly noticeable when the heat collector operates abnormally.

For example, if the heat medium is suddenly passed through the heat medium pipe 2 in a dry firing state where no heat medium is passed through the heat medium pipe 2, the heat medium pipe 2
is unilaterally cooled and tends to contract faster than the heat collecting plate 3. On the other hand, as mentioned above, since the heat medium pipe 2 is fitted and joined to the heat collecting plate 3, a static frictional force proportional to the contact length is acting on this fitted part, and as a result, Conflicting thermal stress occurs between the heat medium pipe 2 and the heat collecting plate 3. That is, a compressive force acts on the heat collecting plate 3, and a tensile force acts on the heat medium pipe 2 and the plate 4 which is made of the same material as the heat medium pipe 2 and is joined to the heat medium pipe 2. This thermal stress increases as the heat transfer pipe 2 contracts, but since there is an upper limit to the static frictional force, the moment the thermal stress overcomes this static frictional force, the heat collecting plate 3 and the contact plate 4 are fixed. A large shear stress is applied directly to the rivet 5 or the caulked portion. Furthermore, if this shear stress is greater than the strength of the rivet or caulked portion, there is a possibility that the rivet or caulked portion may be damaged and the heat collecting plate may be lifted from the heat transfer pipe. This was an extremely serious problem because it was accompanied by a decrease in heat collection efficiency and the aesthetic value of the product was decreased.

The present invention has been made in view of these points, and it is an object of the present invention to provide a solar heat collector that reliably prevents rotation and slippage of the heat collecting plate and eliminates damage to the plate portion due to thermal stress. purpose.

According to the present invention, this purpose is achieved by attaching, by riveting or caulking, a backing plate made of the same material as the heat-transfer pipe to the approximate center of the back surface of the heat collecting plate into which the heat-transfer pipe is inserted, and connecting the backing plate with the heat-receiving plate. This is achieved by joining the medium pipe by brazing or welding. Embodiments of the present invention will be described below based on the drawings.

FIGS. 3 to 4 show an embodiment of the present invention corresponding to FIGS. 1 and 2 explaining the conventional configuration, and the same reference numerals are given to the same parts as in the conventional structure. There is. Reference numeral 1 denotes a light-transmitting outer tube, and a heat medium tube 2 is housed inside. This heat medium pipe 2 has 2
A number of heat collecting plates 3 are fitted at predetermined intervals, and a contact plate 7 made of copper or copper alloy, which is a material similar to that of the heat transfer pipes, is mounted approximately in the center of each heat collecting plate with rivets 5.
Alternatively, it is attached by caulking, and furthermore, the contact plate 7 and the heat medium pipe 2 are joined by welding 6 or brazing.

Compared to the conventional configuration in which two heat collecting plates are connected by one backing plate, one backing plate is installed approximately in the center of each heat collecting plate.
Since the heat collecting plate 3 of the heat medium pipe 2
The stress caused by thermal expansion and contraction of the heat collecting plate 3 acts in opposite directions from both ends with the contact plate 7 as a border so that the stress is zero at both ends of the heat collecting plate 3 and is maximum at the center contact plate. At this time, the forces acting from both ends act to cancel each other out on the heat collecting plate itself, and these two
Since the contact plate 7 is attached approximately at the center of the heat collecting plate 3 where the two forces are in equilibrium, the heat collecting plate 3 and the contact plate 7
Almost no shearing force acts on the rivet 5 or the caulked portion that fixes it.

Furthermore, in the case of this embodiment, since the contact length of the fitting portion between the heat medium pipe 2 and the heat collecting plate 3 corresponding to one contact plate is approximately half of that of the conventional one, the length of contact at the fitting portion of The resulting static friction force is also halved. This means that the force acting between the heat medium pipe 2 and the heat collecting plate 3 becomes smaller, and therefore the force acting on the heat collecting plate itself also becomes smaller.

FIG. 5 shows another embodiment of the present invention, and like FIGS. 1 and 3, it shows a longitudinal cross-sectional view of the heat collector when viewed from the back side. The difference from the above-mentioned embodiment is that the heat collecting plate 8 is composed of a single heat collecting plate 8, and a contact plate 9 is attached approximately at the center thereof. This structure is effective when the heat collecting section is short, and has the advantage of reducing the number of manufacturing steps.

As is clear from the above description, according to the present invention, since the plate serving as a fixing means to the heat medium tube is attached approximately to the center of the heat collecting plate, the force acting between the heat medium pipe and the heat collecting plate is cancel each other out on the heat collecting plate itself, and therefore almost no shearing force acts on the joint between the contact plate and the heat collecting plate. Therefore, the heat collecting plate does not float up, making it possible to maintain high heat collecting efficiency.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of a conventional heat collector with anti-slip structure when viewed from the back side, Fig. 2 is an enlarged view of the conventional contact plate part and its surroundings, and a is a plan view; b shows a side view, and c shows an axial sectional view. Third
The figure is a vertical cross section of a heat collector equipped with a slip prevention structure according to an embodiment of the present invention when viewed from the back side.
The figures are enlarged views of the contact plate part and its surroundings in FIG. 3, where a is a plan view, b is a side view, and c is an axial sectional view. FIG. 5 is another embodiment of the present invention. It is a longitudinal cross-sectional view when the heat collector provided with the anti-slip structure is viewed from the back side. 2... Heat medium pipe, 3, 8... Heat collecting plate, 4, 7, 9... Back plate, 5... Rivet, 6... Brazing.

Claims (1)

[Claims] 1 Approximately in the center of the back surface of the heat collecting plate into which the heat medium tube is inserted,
A solar heat collector characterized in that a plate made of the same material as the heat transfer pipe is attached by riveting or caulking, and the plate and the heat transfer pipe are joined by brazing or welding.