JP3742823B2 - Double-tube solar collector tube and solar collector using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a double-tube solar heat collecting tube that collects solar heat using a heat medium and a solar heat collector using the same.
[0002]
[Prior art]
The use of solar heat is most suitable as a system that generates hot water with low energy levels, and this popularization suppresses the use of fossil fuels and contributes to the reduction of carbon dioxide emissions, resulting in global warming phenomena. It can be a means of deterrence. Conventionally, for example, a method of collecting solar heat by passing or circulating water through a heat collecting tube or box disposed on the roof and heating the water with solar heat has been adopted. There are two types of solar thermal collectors. One is a system where the heat collector and hot water tank are in separate locations and the forced circulation is performed between them by a circulation pump, and the other is that the heat collector and hot water tank are integrated. It is a system that incorporates and circulates naturally. The former is advantageous in that the heat collection efficiency is good and the desired amount of heat collection can be easily obtained, but the installation cost is high. The latter has lower heat collection efficiency than the forced circulation method, but is lower in installation cost.
[0003]
By the way, conventionally, in the solar heat collector used in the above forced circulation method, using a selective absorption film or a vacuum heat insulating glass tube so as not to dissipate the collected heat energy due to the influence of outside air, It has been devised to enhance the heat insulation effect and not dissipate the absorbed energy. For this reason, this heat collector is suitable for a system with a large heat collection scale, a facility that uses hot water continuously throughout the day, or a facility that requires full-scale hot water supply. The equipment is expensive and difficult to install.
[0004]
[Problems to be solved by the invention]
The present invention provides a double-pipe solar heat collecting tube with excellent heat collecting effect, can be used even in a small scale such as an individual house, can be easily installed at low cost, and can also be applied to a forced circulation system. The object is to provide a heater.
[0005]
[Means for Solving the Problems]
The present invention comprises a metal double tube having an outer tube and an inner tube through which a heat medium passes . The space formed by the outer tube and the inner tube is depressurized, and the working heat medium is transferred to the space by receiving solar heat. Is a double-pipe solar heat collecting tube in which a necessary amount is sealed and a non-woven fabric or a net-like wick is stuck on the entire inner surface of the outer tube, and the inner tube is not in contact with the liquid of the working heat medium It is a double-tube solar heat collecting tube characterized by being disposed at a position . The inner tube may be bent in a U shape and disposed in the outer tube. In the present invention, a plurality of the above-mentioned double-tube solar heat collecting tubes are juxtaposed, the inner tubes of the heat collecting tubes are connected in series or in parallel with a connecting tube, and the heat medium is passed through the inner tube. This is a solar heat collector characterized by the above.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a longitudinal sectional view of a double-tube solar heat collecting tube of the present invention, and FIG. 2 is a transverse section of the central portion thereof. 10 is a double-tube solar heat collecting tube, 1 is its outer tube, and 2 is its inner tube. The outer tube 1 is composed of a metal tube. The metal tube is preferably a thin metal tube in order to reduce the weight, and it is preferable to form the unevenness 3 in the circumferential direction so as to have rigidity and strength. The irregularities 3 in the circumferential direction may be spiral or formed on the same circumference. Further, it is preferable to improve the heat absorption efficiency by coloring the outer surface black. Reference numeral 4 denotes a blind plate for closing both ends of the outer tube. Reference numeral 5 denotes a so-called vacuum suction port for reducing the pressure between the outer tube 1 and the inner tube 2. A non-woven fabric or a net-like wick 6 is attached to the inner wall surface of the outer tube 1 over the entire surface. This wick may be made of fibers such as natural fibers and synthetic fibers, or may be made of metal.
[0007]
The inner tube 2 is located at the center of the outer tube, and is composed of a thin metal tube. The inner tube 2 is preferably a helical tube or a bellows tube in order to relieve a difference in expansion and contraction due to a temperature difference from the outer tube 1. An inlet tube 7 and a discharge tube 7 ′ are attached to both ends of the inner tube 2, and the introduction tube 7 and the discharge tube 7 ′ penetrate the blind plate 4 that closes both ends of the outer tube 1, and are airtight to the blind plate 4. It is stuck to. A heat medium such as water is caused to flow into the inner pipe 2 from the introduction pipe 7. This heat medium is indirectly heated by the collected solar heat, and flows out from the discharge pipe 7 'in a heated state. It is preferable that the introduction pipe 7 and the discharge pipe 7 ′ are vacuum double pipes in order to improve heat insulation. Reference numeral 8 denotes a liquid working heat medium injected into the space between the outer tube 1 and the inner tube 2, and this working heat medium can be injected from the vacuum suction port 5. A liquid such as water can be used for the working heat medium 8, and the amount of injection is an amount necessary for the transfer of solar heat, and when there is no transfer of heat, an amount that does not contact the inner tube 2 is enclosed (see FIG. 2). Moreover, it is also possible to attach a flat mirror or a concave mirror to the back surface of the heat receiving surface of the double-tube solar heat collecting tube, and to reflect the solar heat to the back surface of the heat collecting tube to increase the heat receiving area.
[0008]
The operation of the double-tube solar heat collecting tube 10 of the above example will be described. This heat collection tube is leveled and exposed to sunlight. The liquid working heat medium 8 located at the bottom of the double tube is sucked up by capillary action on the inner wall of the outer tube 1 by a wick 6 attached to the inner wall surface of the outer tube 1. In this sucked up state, the working heat medium 8 is heated by solar heat and becomes steam to fill the space between the outer tube 1 and the inner tube 2 of the double tube. At this time, the space between the outer tube 1 and the inner tube 2 is depressurized in order to make the working heat medium easy to be steam (in other words, the space between the outer tube 1 and the inner tube 2 is depressurized, and the depressurization is performed. The boiling point of the working heat medium is adjusted to the extent of The filled steam is cooled by a heat medium such as water flowing in the inner pipe 2 (the heat medium is heated reversely), condensed on the surface of the inner pipe 2, and dropped to return to the bottom of the double pipe. To do. Thus, as a result, the radiant heat radiated from the sun is collected by the heat collecting mechanism of the double tube and stored as heat in the heat medium flowing in the inner tube 2. With respect to the working heat medium 8, the amount necessary for giving and receiving solar heat means an amount necessary for sufficiently exhibiting the above action. The heat stored in the heat medium can be used by various conventionally known methods. For example, when water is used as the heat medium, the heated water may be used as it is for a bath or the like, or may be used for a hot water supply or a heating system in combination with an auxiliary boiler, a heat exchanger, or the like.
[0009]
Further, in cloudy weather or nighttime when the sun is hidden, the radiant heat of the sun that reaches the surface of the outer tube 1 is blocked, and the temperature of the wick 6 that is in close contact with the inner surface of the outer tube 1 drops. As a result, the steam of the working heat medium, which has existed in the space between the outer tube 1 and the inner tube 2 until now, moves in the condensation location due to the balance between the surface temperature of the inner tube 1 and the temperature of the wick 6. It moves from the surface of the tube 2 to the wick 6 having a low temperature. This is because the lower the surface temperature of the outer tube 1 of the double-tube solar heat collecting tube 10, the higher the degree of vacuum inside the tube, and the less susceptible to changes in the temperature of the inner tube 2, and the soot is kept warm from the outside air. Will be in the situation. In this double-tube solar heat collecting tube 10, the inner tube 1 and the outer tube 2 are in contact with each other at the end surface of the outer tube 1. In some cases, the temperature of the heat medium in the tube 2 is lowered, causing a phenomenon such as freezing. In order to avoid this phenomenon, as described above, the introduction pipe 7 and the discharge pipe 7 ′ at both end portions where the end face of the outer pipe 1 and the inner pipe 2 are in contact with each other serve as a vacuum heat insulating pipe and affect the temperature change of the outer pipe. It is preferable that the structure not be used.
[0010]
In the above example, a single double-pipe solar heat collecting tube 10 has been described. However, in order to increase the amount of heat collection, a plurality of double-pipe solar heat collecting tubes 10 are installed in parallel. The tubes may be coupled in series or in parallel with a coupling tube. FIG. 3 shows an example when the double-tube solar heat collecting tube 10 is coupled by the coupling tube 11. Reference numeral 12 denotes a tube for allowing a heat medium such as water to flow into the inner tube 2, and reference numeral 13 denotes a tube for discharging the heat medium from the inner tube 2. In this example, two double-tube solar heat collecting tubes 10 are connected, but two or more may be connected. In this way, a plurality of the double-tube solar heat collecting tubes 10 are juxtaposed (in this case, it is preferable to arrange the tubes so that each tube is horizontal), and the inner tubes of the heat collecting tubes are connected to each other. A solar heat collector can be created by connecting in series or parallel with the connecting pipe 11 and passing a heat medium through the inner pipe 2. It is also possible to attach a flat mirror or a concave mirror to the back surface of the heat receiving surface of the solar heat collector to increase the heat receiving area by reflecting solar heat to the back surface of the heat collecting tube. In addition, by adopting a vacuum heat insulating tube as the above-described coupling tube 11, heat radiation from the entire solar heat collection system can be suppressed as much as possible, and a system that does not use extra energy for measures such as freezing in winter can be achieved. .
[0011]
FIG. 4 is a longitudinal sectional view of another example of the double-tube solar heat collecting tube of the present invention, and FIG. 5 is a transverse section of the central portion thereof. 20 is a double-pipe solar heat collecting tube, 21 is its outer tube, and 22 is its inner tube. The outer tube 21 is composed of a metal tube. The metal tube is preferably a thin metal tube in order to reduce the weight, and it is preferable to form the unevenness 23 in the circumferential direction so as to have rigidity and strength. The unevenness 23 in the circumferential direction may be spiral or formed on the same circumference. Further, it is preferable to improve the heat absorption efficiency by coloring the outer surface black. A blind plate 24 closes both ends of the outer tube. Reference numeral 25 denotes a so-called vacuum suction port for reducing the pressure between the outer tube 21 and the inner tube 22. A nonwoven fabric or a net-like wick 26 is attached to the inner wall surface of the outer tube 21.
[0012]
The inner tube 22 is located at the center of the outer tube 21 and is formed of a thin metal tube. The inner tube 22 enters from one end of the outer tube 21, is bent into a U shape near the other end, and comes out of the same end again. The inner tube 22 can be a smooth tube, a helical tube or a bellows tube. In the case of the double-tube solar heat collecting tube having this structure, the inner tube 22 is only fixed to one end of the outer tube 21, so that the outer tube and the inner tube are connected as in the case of the heat collecting tube of FIG. There is no need to take into account shrinkage differences due to temperature differences. An introduction pipe 27 and a discharge pipe 27 ′ are attached to both ends of the inner pipe 22. The introduction pipe 27 and the discharge pipe 27 ′ pass through a blind plate 24 that closes the end of the outer tube 21, and each of the blind plates 24 is airtight. Is stuck. A heat medium such as water is caused to flow from the introduction pipe 27 into the inner pipe 22. This heat medium collects and warms the sun, that is, is heated and flows out of the discharge pipe 27 '. It is preferable that the introduction pipe 27 and the discharge pipe 27 ′ are vacuum double pipes in order to improve heat insulation. Reference numeral 28 denotes a liquid working heat medium injected into the space between the outer tube 21 and the inner tube 22, and this working heat medium can be injected from the vacuum suction port 25. The working heat medium 28 is water or the like, and its injection amount is an amount necessary for the transfer of solar heat, and an amount that does not contact the inner tube 22 when no heat is transferred (see FIG. 2). Moreover, it is also possible to attach a flat mirror or a concave mirror to the back surface of the heat receiving surface of the double-tube solar heat collecting tube, and to reflect the solar heat to the back surface of the heat collecting tube to increase the heat receiving area.
[0013]
The double-pipe solar collector tube shown in FIGS. 4 and 5 collects solar heat by the same action as the double-pipe solar collector tube described in FIGS. Therefore, a solar heat collector can be made using this double-tube solar heat collecting tube. In FIG. 4, the single double-pipe solar heat collecting tube 20 has been described. However, in order to increase the amount of heat collection, a plurality of the double-pipe solar heat collecting tubes 20 are installed in parallel. The tubes may be coupled in series or in parallel with a coupling tube. FIG. 6 shows an example when the double-pipe solar heat collecting tube 20 is coupled by the coupling tube 11. Reference numeral 12 denotes a tube for allowing a heat medium such as water to flow into the inner tube 22, and reference numeral 13 denotes a tube for discharging the heat medium from the inner tube 22. In this example, two double-tube solar heat collecting tubes 20 are connected, but two or more may be connected. In this way, by arranging a plurality of the double-tube solar heat collecting tubes 20 in parallel, connecting the inner tubes of the heat collecting tubes in series or in parallel with the connecting tube 11, and passing the heat medium through the inner tube 2 Can create a solar collector. It is also possible to attach a flat mirror or a concave mirror to the back surface of the heat receiving surface of the solar heat collector to increase the heat receiving area by reflecting solar heat to the back surface of the heat collecting tube.
[0014]
【The invention's effect】
As described above, in the present invention, the steam of the working heat medium generated by absorbing solar heat in a small amount of the working heat medium is cooled by a heat medium such as water, and the latent heat of the working heat medium is recovered. Since it is a system that absorbs heat into a cooling heat medium, the structure is simple, the manufacturing cost is low, and it is lightweight, so it can be used for general purposes. This is advantageous in that it can be applied from a small-scale system to a large-scale system because it is not limited in scale in the construction of a solar heat utilization system.
[Brief description of the drawings]
FIG. 1 is a vertical cross-sectional view of a double-tube solar collector tube according to the present invention. FIG. 2 is a cross-sectional view of a double-tube solar collector tube according to the present invention. FIG. 4 is a longitudinal sectional view of another example of the double-pipe solar collector tube of the present invention. FIG. 5 is a cross-sectional view of another example of the dual-pipe solar collector tube of the present invention. FIG. 6 is a cross-sectional view of another example when the double-pipe solar collector tube of the present invention is connected.
1,21 Outer tube, 2,22 Inner tube, 3,23 Convex part, 4,24 Blind plate, 5,25 Vacuum outlet, 6,26 Wick, 7,27 Heat medium introduction tube, 7 ', 27' Heat Medium discharge pipe, 8,28 Working heat medium, 10,20 Double pipe solar collector tube, 11 Coupling pipe, 12,13 tube

Claims (3)

It consists of a metal double tube with an outer tube and an inner tube through which the heat medium passes , and the space composed of the outer tube and the inner tube is depressurized, and the amount of working heat medium necessary for receiving and receiving solar heat in the space And a double-tube solar heat collecting tube in which a non-woven fabric or a net-like wick is attached to the entire inner surface of the outer tube, and the inner tube is disposed at a position where it does not contact the liquid of the working heat medium. A double-tube solar collector tube, characterized by 2. The double-tube solar collector tube according to claim 1, wherein the inner tube is bent in a U shape and disposed in the outer tube. A plurality of the double-pipe solar heat collecting tubes according to claim 1 or 2 are juxtaposed, the inner tubes of the heat collecting tubes are connected in series or in parallel with a connecting tube, and the heat medium is passed through the inner tube. A solar heat collector characterized by that.

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