JPS637308B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solar heat collector, and is intended to prevent dew condensation on the inside of a light-transmitting cover that forms a light-receiving surface.

Generally, a solar heat collector is constructed as shown in FIG. That is, a case 2 in which a heat insulating material 1 is disposed on the inner bottom and the inner side, a heat collecting plate 3 provided on the heat insulating material 1 in the inner bottom and configured to flow a heat medium such as water, and the heat collecting plate 3, It is comprised of a transparent cover 4 made of glass or the like that forms a closed space between it and the hot plate 3 and serves as a light receiving surface.

In addition, in the figure, 5 is a sealing material provided at the attachment part of the transparent cover 4, 6 is a retainer for holding the transparent cover 4, 7 is an inner frame member, and 8 is a convection prevention material provided in the closed space. The transparent film 9 and 10 are an inflow pipe and an outflow pipe for the heat medium. Further, a selective absorption film is provided on the surface of the heat collecting plate 3, and the transparent film 8 is also made of a material having selective absorption properties.

In the above configuration, sunlight passes through the light-transmitting cover 4 and further passes through the light-transmitting film 8 to reach the heat collecting plate 3, and heats the heat medium by heating the heat collecting plate 3. When there is no sunlight, energy cannot be obtained from sunlight, so the flow of the heat medium is stopped by appropriate control means.

By the way, the temperature drops from after sunset until sunrise. Therefore, the temperature difference between the air inside the collector and the outside air causes condensation inside the collector. In this dew condensation, the condensation on the inner surface of the transparent cover 4 is particularly noticeable. In other words, since the heat insulating material 1 is arranged on the bottom and side surfaces of the inside of the heat collector, the heat flux in the insulating material 1 is small, while the transparent cover 4 made of glass or the like has a higher heat transmission rate than the heat insulating material 1. The heat flux in the transparent cover 4 is larger than the heat flux in the heat insulating material 1.
Therefore, the temperature of the air in contact with the inner surface of the light-transmitting cover 4 is lower than the temperature of the air in contact with the inner surface of the heat insulating material 1, and dew condensation is more likely to occur on the inner surface of the light-transmitting cover 4 than on the inner surface of the heat insulating material 1.

To explain the above on the psychrometric diagram shown in Figure 2, the air near the inner surface of the transparent cover 4 is at point A when there is sunlight during the day, but after sunset the temperature drops. When the absolute humidity x is constant, the temperature reaches point B (dew point), and then moves along the saturation line to point C. At this time, moisture equivalent to the decrease in absolute humidity x is discharged and adhered to the inner surface of the transparent cover 4. The water adhering to the light-transmitting cover 4 spreads out in a planar shape depending on the condition of the inner surface of the light-transmitting cover 4, and a large amount of water adhering falls due to gravity and may even fall onto the light-transmitting film 8. These waters reflect sunlight well, and therefore, assuming other conditions are the same, the energy obtained when the heat medium passes through the heat collecting plate 3 is less than when no dew condensation occurs. Therefore, as a result, heat collection efficiency decreases.

The present invention aims to solve the above-mentioned conventional problem of condensation and provide a solar heat collector with high heat collection efficiency, and will be described below with reference to FIG. 3 showing one embodiment. In FIG. 3, each component numbered 1 to 10 denoted by the same reference numerals as in FIG. 1 is constructed in the same manner as in FIG.

The feature of the present invention is that the heat pipe 11
The reason is that we have prepared the following. The heat pipe 11 passes through the case 2 and the heat insulating material 1, has one end 11a looking into the closed space 12 closed by the transparent cover 4, and the other end 11b looking outside the case 2,
I have Uitsuku. The end portion 11b of the heat pipe 11 facing outside the case 2 is the other end 11b.
heat pipe 1 so that it is located below a.
1 is installed in a diagonal manner. This heat pipe 11 is held by a holding member 13 having a suitable pipe shape, and a gap sufficient for water droplets to fall along the outer periphery is provided.

The heat collecting operation of the solar heat collector of the present invention having the above configuration is the same as that described above with reference to FIG. 1. However, when there is no sunlight and the air in the closed space 12 is cooled, such as at night, a characteristic operation occurs. That is, the heat pipe 11 has a wick, and its thermal resistance to heat transfer from above to below is much smaller than other conductive members, and it has a smaller thermal resistance than the transparent cover, which has a larger surface area than the heat pipe 11. , the temperature of the inner end 11a is lower than the temperature of the inner surface of the transparent cover 4. Therefore, moisture in the closed space 12 tends to adhere to and condense on the inner end 11a of the heat pipe 11. The water condensed on the surface of the heat pipe 11 is transmitted along the surface of the heat pipe 11 by gravity to the outer end 11.
After moving to b, it falls outside. For this reason,
Condensation is less likely to occur on the inner surface of the transparent cover 4, and as a result, heat collection efficiency is not reduced.

Further, it is preferable that the portion of the heat pipe 11 exposed to the outside air be coated with a black coating 14 having a high emissivity. That is, when the outside air temperature decreases at night, the temperature at the outer end 11b of the heat pipe 11 decreases due to the radiation cooling effect compared to when there is no black coating, and easily becomes equal to or lower than the inner surface temperature of the transparent cover 4. Therefore, the outer end 11b of the heat pipe 11
The emissivity of the paint applied to the transparent cover 4 is the emissivity of the transparent cover 4 in the thermal radiation wavelength region near room temperature (for ordinary glass
(approximately 0.8 to 0.9), the inner surface temperature of the transparent cover 4 will easily drop below the temperature due to the radiation cooling effect.
Therefore, the aforementioned effect of preventing condensation is further promoted. Further, when there is sunlight during the day, the outer end 11b of the heat pipe 11 is black and therefore absorbs sunlight well, and the temperature rises, so that heat is prevented from flowing out from the closed space 12 through the heat pipe 11. The above-mentioned paint is often found in commercially available matte black paints, and has an absorption rate of about 0.95 and an emissivity of about 0.95.

Although only one heat pipe 11 is shown in the embodiment, the effect of preventing condensation can be improved by increasing the number of heat pipes 11 or by considering the length of the heat pipe 11 in the portion that contacts the outside air. Needless to say, it will become larger. Also, when the outer end 11b of the heat pipe 11 is placed in thermal contact with the outer part of the case 2, the case 2
The outer part of the air has a similar effect because it is at a temperature close to the air temperature.

As explained above, the present invention is equipped with a heat pipe, and when the outside temperature drops such as at night, the heat pipe actively causes dew condensation in the closed space of the heat collector, thereby preventing dew condensation on the transparent cover, etc. prevent,
It does not reduce heat collection efficiency and has great value.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional solar heat collector, FIG. 2 is a psychrometric diagram, and FIG. 3 is a sectional view of a solar heat collector according to an embodiment of the present invention. 1...Insulating material, 2...Case, 3...Heat collecting plate,
4... Transparent cover, 8... Transparent film, 11... Heat pipe, 12... Closed space, 14... Black paint.

Claims (1)

[Claims] 1. A solar heat collector equipped with a heat collecting plate inside and having a closed space with a transparent cover,
A heat pipe is provided, one end of which looks into the closed space, the other end of which is located below the one end and looks into the outside air, and a gap is provided at least below the heat pipe with a wall of the closed space. A solar heat collector. 2. Claim 1, characterized in that the end of the heat pipe that looks into the outside air is painted black.
Solar thermal collectors as described in section.