JPS6033219B2 - Vacuum tube solar collector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum tube type solar collector comprising a heat collector tube provided with a vacuum heat insulating layer and a reflecting plate.

In order to increase the efficiency of solar heat collectors, it is necessary to increase the sunlight transmittance of the transparent cover that covers the heat receiving part and the sunlight absorption rate of the heat receiving part, and reduce heat loss due to conduction, convection, and solar radiation from the heat receiving part. There is a need to.

As a means of reducing heat loss due to conduction and convection, it has been considered to create a structure in which the inside of a transparent glass tube is evacuated and a heat collecting plate is provided therein. Furthermore, as a means to reduce heat loss due to radiation, a so-called selective absorption film, which has a low emissivity at infrared wavelengths, is usually used on the surface of the heat collecting plate. This type of collector is called a vacuum glass tube type solar collector, and the glass tube is usually used to increase the pressure resistance of the cylindrical shape. Figures 1 and 2 show a conventional vacuum tube type solar collector tube, in which 1 is a transparent glass tube, 2 is a heat collector plate with a colored aluminum selective absorption film made by anodizing, Reference numeral 3 denotes a heat medium pipe that is in direct contact with the heat collecting plate 2, and this heat medium pipe 3 is made of a metal pipe such as a steel pipe.

Reference numeral 4 denotes an inlet/outlet portion of the heat medium pipe 3, which is provided to take out the heat collected by the heat collecting plate 2 to the outside of the heat collector.

Reference numeral 5 denotes a connecting portion between the transparent glass tube 1 and the heat medium inlet/outlet portion 4, and this connecting portion 5 is completely sealed after evacuation in order to maintain the inside of the transparent glass tube 1 in a vacuum.

Examples in which a plurality of such evacuated heat collecting tubes are arranged side by side are shown in FIGS. 3 and 4. Fig. 3 shows an example in which vacuum tube type heat collecting tubes 6 are arranged relatively densely.In this case, the amount of heat collected per unit installation area of the heat collector is large, but it is economically expensive because a large number of heat collecting tubes 6 are arranged side by side. It also depends on the inclination of the heat collecting plate 7, but in winter, when the angle of incidence of sunlight is low, the adjacent heat collecting plate There was a drawback that the heat collection plate was in the shade, and as a result, the amount of heat collected per unit area of the heat collection plate was low. On the other hand, in FIG. 4, a semicircular reflecting mirror 9 is provided below the heat collecting tube 8 to eliminate the two drawbacks in FIG. 3.

As for the shape of the reflecting mirror 9, many other shapes have been proposed, such as a flat plate and a trocogle curved surface. However, in the normal case where the reflecting mirror 9 is used, sunlight is received on both the front and back sides of the heat collecting plate 10, so it is necessary to apply selective absorption films to both sides of the heat collecting plate 10. However, the emissivity of the selectively absorbing surface is larger than that of the metal surface, and as a result, by doubling the selectively absorbing surface, the radiation loss of the collected heat nearly doubles. Therefore, even if the reflecting mirror 9 is provided, the effect is not so great. The present invention reduces the number of relatively expensive evacuated glass tube type heat collecting tubes and uses a relatively inexpensive reflecting plate, thereby improving the spacing between the heat collecting tubes arranged side by side.
The aim is to obtain an inexpensive and high-performance vacuum tube type solar heat collector by optimizing the slope of the heat collector plate, the installation location and shape of the reflector plate, etc.

That is, the inclination of the heat collecting plate is made relatively large in accordance with the low solar inclination during winter, and the interval between adjacent heat collecting pipes is also slightly increased so as not to shade the neighboring heat collecting pipes.

In addition, since the angle of incidence of sunlight is large outside of winter, in the method of placing them side by side with large intervals as described above, the sunlight in the area between adjacent heat collection tubes will pass through as is, so the light in this area will be The reflective plate allows the reflected light to hit the front side of the heat collecting plate of adjacent heat collecting tubes. At this time, by carefully arranging the position of the reflector so that the sunlight would not be blocked by the reflector even in winter, we were able to obtain an inexpensive and high-performance vacuum tube type solar collector. be. Hereinafter, the present invention will be explained based on drawings showing embodiments thereof. As shown in FIG. 5, a transparent glass tube 11 with a diameter of 100 mm and a thickness of 1. A plurality of heat collecting pipes 14 are installed at intervals on the 52 side, each consisting of a heat collecting plate 12 made of aluminum and a heat medium pipe 13 made of two steel pipes having an outer diameter of 9.53 mm. The books were placed side by side on a nearly flat roof 16. The width of the heat collecting plate 12 was 9 degrees, and the angle was 35 degrees with respect to the horizontal line. Further, a reflective plate 15 made of an aluminum plate was provided between adjacent heat collecting tubes 14. The width of this reflecting plate 15 is on the 56 side, and the inclination is about 3 with respect to the horizontal line.
The distance between adjacent heat collecting tubes 14 is approximately 5 degrees, and the reflecting plate 15 is in the form of a flat plate, and its reflectance is 80%.
For comparison, a number of trial heat collectors were fabricated in which the distance between adjacent heat collection tubes 14 and the angle of heat collection plates 12 were changed.

Next, these heat collectors were measured, and the optimum values for the spacing between adjacent heat collecting tubes 14, the head slope of the heat collecting plate 12, etc. were determined at a point of 35o north latitude based on the heat collection ratio.

The amount of heat collected is measured under a water temperature difference of 50 qo from the outside air, and 1
The heat collection ratio was calculated by dividing the annual total heat collection by the heat collector installation area. FIG. 6 shows the influence of the interval between adjacent heat collecting tubes 14 when the inclination of the heat collecting plate 12 is 35 degrees. The angle of inclination of the reflector 15 was set to an optimum value, and the width of the reflector 15 was determined so as to maintain a distance of five ribs from the heat collecting tube 14. As is clear from this FIG.
Particularly good results were obtained within the range of . Also, this means that
If the installation interval of the heat collecting pipes 14 is too large, it means that it cannot be compensated for by the reflector plate 15, and conversely, if the interval is too small, a large number of collecting pipes will be required, which will be expensive, and the front heat collecting pipe will not be placed in the shade. This means that the amount of heat collected decreases. In addition, regarding the inclination angle of the reflection plate 15,
The optimum value varies depending on the interval between the heat collecting tubes 14, the measurement point, etc., but as a rough guide, a range of 20 to 60 degrees is suitable.

A particularly effective range is 30 to 50 degrees. Furthermore, by setting the distance between the reflecting plate 15 and the heat collecting pipe 14 within a range of 1 to 1 distance, dirt, dust, leaves, etc. that tend to accumulate on the reflecting plate 15 and the heat collecting pipe 14 can be removed by rain or wind. It was found that this did not pose a major problem in practice. Furthermore, the reflective plate 15
By locating the heat collecting plates 12 below the line connecting the upper ends of each of the heat collecting plates 12, sunlight is no longer blocked by the reflecting plates 15 even in winter.
Regarding the shape of the reflecting plate 15, from the viewpoint of manufacturing, it is most preferable to have a flat plate, but it may also have a concave shape.

As described above, according to the present invention, a reflecting plate is provided between adjacent heat collecting tubes so that the upper surface and the reflective surface of the heat collecting plate in a plurality of heat collecting tubes arranged in a row are in an upwardly open state. As a result, an inexpensive and high-performance vacuum tube type solar heat collector can be obtained.

[Brief explanation of the drawing]

Figure 1 is a cutaway front view of a collector tube used in a conventional evacuated tube type solar collector, Figure 2 is a sectional view taken along line A-A in Figure 1, and Figures 3 and 4 are a side-by-side arrangement of the collector tubes. Schematic diagram illustrating the method;
FIG. 5 is a side sectional view of a vacuum tube type solar heat collector showing an embodiment of the present invention, and FIG. 6 is a characteristic diagram showing the relationship between the heat collecting tube interval and the heat collection ratio of the same heat collector. 11...Transparent glass tube, 12... Heat collecting plate,
14... Heat collection tube, 15... Reflection plate. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1. A plurality of heat collecting tubes each having a heat collecting plate arranged in an inclined manner inside a transparent glass tube whose interior is maintained in a vacuum state,
In a vacuum tube type solar heat collector installed on a substantially flat roof, a reflector plate is placed between adjacent heat collector tubes so that the upper surface and reflective surface of the heat collector plate in the heat collector tubes are open upward. A vacuum tube type solar heat collector characterized by the following: 2. The evacuated tube type solar heat collector according to claim 1, wherein the reflecting plate is located below a line connecting the upper ends of each heat collecting plate in adjacent heat collecting tubes. 3 The interval between the adjacent heat collecting pipes is set to 1/4 of the diameter of the heat collecting pipes.
The evacuated tube type solar heat collector according to claim 1 or 2, which is within the range of 1/1 to 1/1. 4. The vacuum tube type solar heat collector according to any one of claims 1 to 3, wherein the reflecting plate is installed within a range of 20 to 60 degrees with respect to the horizontal line. 5. The evacuated tube solar heat collector according to any one of claims 1 to 4, wherein the interval between the reflecting plate and the heat collecting tube is within a range of 1 to 10 mm.