JP2012145288A - Solar heat collector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce thermal stress between a casing of a solar heat collector and piping in which a heat medium flows.SOLUTION: This solar heat collector 10 includes the casing 11, a heater 12 for heating the heat medium, and a connecting device 20 disposed in a state of penetrating through a wall of the casing. The connecting device 20 includes an inner pipe 21 in which a high-temperature heat medium flows, and an outer pipe 22 connected to the wall of the casing 11 at its outer face to allow a low-temperature heat medium to flow between the outer pipe and an outer face of the inner pipe 21. The outer pipe 22 is connected to the outer face of the inner pipe 21 at a casing inner side end 23 and a casing outer side end 24, and nozzles 25, 26 for circulating the low-temperature medium, are disposed on the outer faces at the inner side and an outer side, of the casing 11.

Description

  The present invention relates to the structure of a solar thermal collector.

  It is underway to collect solar heat and use the heat to heat the heating medium and extract the energy. As a device for collecting solar heat into a high-temperature heat medium, a heat collector is placed on a high tower and the heat medium is heated to a high temperature by collecting sunlight using about 1000 plane mirrors. There were a tower method and a method in which a heat collecting tube was arranged at the focal position of a cylindrical parabolic mirror and a heat medium flowing through the heat collecting tube was heated. However, these methods have a problem that the whole system becomes large and a special mirror is required.

  For this reason, a heat collector with a selective absorption film with wavelength selectivity that absorbs energy in the wavelength band centered on visible light is placed in a casing whose inside is vacuumed, and the outside is exposed by air. There has been proposed a solar heat collecting apparatus in which loss due to heat conduction to the light and radiation loss in the far infrared region are reduced (see, for example, Patent Document 1). In the solar heat collecting apparatus described in Patent Document 1, water as a heat medium is passed through a heat collector, and the water is heated to extract heat energy to the outside. Water inlets and outlets are provided so as to penetrate the wall surface of the vacuum casing, and normal temperature water flowing from the inlet into the heat collector inside the casing is heated from about 120 ° C. to about 300 ° C. Being configured to come out from the exit.

JP 2002-115717 A

  The solar collector collects sunlight during the daytime and raises the temperature of the heat collector outlet heat medium from 120 ° C to 300 ° C, but when the sun goes down at night, the temperature of the heat collector outlet heat medium increases. It will return to room temperature. For this reason, the temperature of the piping at the outlet of the heat medium of the heat collector changes greatly between day and night, and this temperature change changes the outer diameter of the piping, and a large repetitive stress is applied to the casing. . If this repeated stress causes damage between the casing and the piping at the outlet of the heat medium or on the casing wall, the vacuum inside the casing is broken, heat loss increases due to heat conduction to the outside by the air that enters, and solar heat There was a problem that the heat collection efficiency of the collector was lowered.

  An object of this invention is to reduce the thermal stress between the casing of a solar-heat collector and piping which flows a heat carrier.

  The solar collector of the present invention is attached to the casing, the heater that heats the heat medium that flows inside by the heat from sunlight, and the casing that penetrates the wall of the casing and is heated by the heater. A solar heat collector comprising a low temperature heat medium before heating and a high temperature heat medium heated by a heater between the inside and the outside of the casing, wherein the connection apparatus is a high temperature heat medium And an outer pipe whose outer surface is connected to the wall of the casing and a low-temperature heat medium flows between the outer surface of the inner pipe and the outer pipe at the casing inner side end and the casing outer side end. Each of the nozzles is connected to the outer surface of the inner tube, and has a nozzle through which a low-temperature medium circulates on the inner surface and the outer surface of the casing.

  In the solar collector of the present invention, the outer tube gradually decreases in outer diameter toward the casing inner side end and the casing outer side end, and the casing inner side end of the outer tube and the casing outer side end of the outer tube are: It is also preferable that the inner surface of the outer tube is connected so as to overlap the outer surface of the inner tube.

  Further, in the solar collector of the present invention, the outer tube can extend or contract in the longitudinal direction between the casing wall and the casing inner side end or between the casing wall and the casing outer side end or both. It is also suitable as including an elastic part.

  The present invention has an effect of reducing the thermal stress between the casing of the solar heat collector and the piping through which the heat medium flows.

It is explanatory drawing which shows the solar-heat collection system incorporating the solar-heat collector in embodiment of this invention. It is explanatory drawing which shows the solar collector in embodiment of this invention. It is explanatory drawing which shows the connection apparatus of the solar-heat collector in other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, a solar heat collecting system incorporating the solar heat collector of the present invention will be described with reference to FIG. As shown in FIG. 1, the solar heat collection system 100 includes a solar heat collector 10 and a reflecting mirror 41. The solar collector 10 is in close contact with the casing 11 that holds the inside in a vacuum, the window glass 14 provided on the lower surface of the casing 11, the heat collector 13 provided inside the casing 11, and the back surface of the heat collector 13. The heater 12, the heat medium supply pipe 33 that supplies a low-temperature heat medium at room temperature to the heater 12, and the heat medium outlet pipe 34 that takes out the high-temperature heat medium heated by the heater 12 are provided. The heat medium supply pipe 33 and the heat medium outlet pipe 34 are connected to the connection device 20 that passes through the casing 11 and distributes the low temperature heat medium and the high temperature heat medium between the inside and the outside of the casing 11. The reflecting mirror 41 is attached to a support member 42, and the support member 42 is attached to the rotation shaft 44 by an arm 43. The rotating shaft 44 is connected to the position adjuster 50. Since the angle of the sun changes depending on the season and time, the rotating shaft 44 is rotated by the position adjuster 50 according to the change of the position of the sun, and the position of the reflecting mirror 41 is changed to efficiently heat the sunlight. It is configured to collect energy.

  The casing 11 is made of a metal material such as iron having the same thermal expansion coefficient as that of the window glass 14. Further, the connection device 20 is made of the same metal material as the casing 11, for example, iron. The surface of the solar collector 13 of the solar collector can efficiently absorb the light energy in the visible region of the sunlight 18, and the far-infrared emissivity from the surface where the temperature has risen is low, so that the radiation loss can be suppressed. An absorption membrane is attached. The heater 12 is attached so that a thin tube through which a heat medium flows is in close contact with the back surface of the heat collector 13.

  FIG. 2 is a view showing the internal structure of the casing 11 of the solar heat collector 10 and the vicinity of the connection device 20 of the present embodiment. In FIG. 2, the structure inside the casing is schematically shown. As shown in FIG. 2, the metal connecting device 20 includes a cylindrical straight pipe inner tube 21 through which a high-temperature heat medium flows, and an outer surface thereof connected to a wall 11 a of the metal casing 11. It is a double tube including an outer tube 22 through which a low-temperature heat medium flows between the outer surfaces. The outer pipe 22 has a central portion 22a connected to the wall 11a of the casing 11 and is a cylindrical straight pipe. The outer surface of the central portion 22a on the outer side of the casing 11 has a low temperature heat connected to the heat medium supply pipe 33. A medium inlet nozzle 26 is provided, and a low temperature heat medium outlet nozzle 25 connected to a heater inlet pipe 15 that supplies a low temperature heat medium to the heater 12 is provided on the outer surface on the inner side of the casing. The outer tube 22 has a tapered portion 27 whose outer diameter gradually decreases from the central portion 22a toward the casing inner side end 23, and a straight portion whose inner surface is fitted to the outer surface of the inner tube 21. 29. Similarly, the outer tube 22 has a tapered portion 28 whose outer diameter gradually decreases from the central portion 22a toward the casing outer side end 24, and a straight line whose inner surface is fitted to the outer surface of the inner tube 21. Part 30. The outer tube 22 is fixed to the outer surface of the inner tube 21 by these two straight portions 29 and 30. A heater outlet pipe 16 through which a high-temperature heat medium from the heater 12 flows is connected to a casing inner side end 31 inside the casing 11 of the inner pipe 21, and a heat medium outlet 32 is connected to a casing outer side end 32 outside the casing 11. A tube 34 is connected.

  Operation | movement of the solar-heat collector 10 comprised as mentioned above is demonstrated. The sunlight 18 is reflected by the surface of the reflecting mirror 41 shown in FIG. 1, enters the inside through the window glass 14 on the lower surface of the solar collector 10, and strikes the heat collector 13 as shown in FIG. 2. The heat collector 13 efficiently collects the heat of the sunlight 18 by the selective absorption film on the surface, and the temperature rises. This heat raises the temperature of the heater 12 that is in close contact with the back surface of the heat collector 13. On the other hand, the room-temperature low-temperature heat medium supplied from the heat medium supply pipe 33 passes from the low-temperature heat medium inlet nozzle 26 of the connection device 20 outside the casing 11 as indicated by an arrow A to the central portion 22a of the outer pipe 22 and the inner pipe. 21 flows into the annular flow path between the two. The low-temperature heat medium flows through the annular flow path from the outside of the casing 11 to the inside, and flows out from the low-temperature heat medium outlet nozzle 25 inside the casing 11 to the heater inlet pipe 15 as indicated by an arrow A. The low-temperature heat medium is introduced into the heater 12 by the heater inlet pipe 15, and the temperature rises in the heater 12 whose temperature has risen, for example, becomes a high-temperature heat medium of about 120 ° C. and is heated from the heater 12. It flows out into the vessel outlet pipe 16. The high-temperature heat medium flows out from the casing inner side end 31 of the inner pipe 21 of the connecting device 20 from the heater outlet pipe 16 to the outside of the casing 11 as indicated by an arrow B, and is connected to the casing outer side end 32. It flows out to the outlet pipe 34. The high-temperature heat medium flowing out to the heat medium outlet pipe 34 transmits heat to an external device such as a heat exchanger (not shown) to supply solar heat energy to the external device.

  In the connection device 20 of the present embodiment, the high-temperature heat medium flows through the inner tube 21, and the low-temperature heat medium flows through the annular flow path between the outer surface of the inner tube 21 and the inner surface of the outer tube 22. The outer diameter of the central portion 22a of the attached outer tube 22 is almost constant regardless of the temperature of the high-temperature heat medium. For this reason, almost no thermal stress is generated between the outer tube 22 and the wall 11 a of the casing 11. For this reason, damage to the casing 11 is suppressed, and the vacuum state inside the casing 11 is also well maintained.

  On the other hand, the temperature of the inner tube 21 through which the high temperature heat medium flows becomes higher than the temperature of the outer tube 22, but since the low temperature heat medium flows through the outer surface, the average temperature of the metal portion of the metal inner tube 21 is high temperature heat. Although the temperature is lower than the temperature of the medium, the temperature is higher than the average temperature of the metal portion of the outer tube 22 through which the low-temperature heat medium flows. For this reason, the amount of thermal expansion in the longitudinal direction of the inner tube 21 is larger than the amount of thermal expansion in the longitudinal direction of the outer tube 22. As a result, a thermal stress in the longitudinal direction is generated between the inner tube 21 and the outer tube 22. A compressive stress is applied to the inner tube 21 whose temperature is high, and a tensile stress is applied to the outer tube 22 whose temperature is low in the longitudinal direction. However, the outer tube 22 is fitted and fixed so that the inner surfaces of the straight portions 29 and 30 near both ends 23 and 24 overlap the outer surface of the inner tube 21, and the straight portions 29 and 30 and the central portion 22a are fixed. Since the taper portions 27 and 28 whose outer diameter gradually changes in the longitudinal direction are provided between them, the generated thermal stress is not concentrated on the connection portion between the inner tube 21 and the outer tube 22. It is configured. Therefore, in the embodiment, even when the temperature of the low temperature heat medium is, for example, about 20 ° C. and the temperature of the high temperature heat medium is, for example, about 120 ° C., thermal stress is applied to the connection portion between the inner tube 21 and the outer tube 22. Without concentrating, the temperature difference between the average temperature of the metal portion of the inner tube 21 and the average temperature of the metal portion of the outer tube 22 is smaller than the temperature difference between the low temperature heat medium and the high temperature heat medium. be able to. For this reason, even if the temperature of the high-temperature heat medium changes between a room temperature of about 20 ° C. and a high temperature of about 120 ° C., the inner tube 21 and the outer tube 22 of the connection device 20 are prevented from being damaged due to repeated fatigue. Is done.

  Another embodiment of the present invention will be described with reference to FIG. Parts similar to those of the embodiment described above with reference to FIGS. 1 and 2 are denoted by the same reference numerals and description thereof is omitted. In the present embodiment, a plurality of bellows portions 35 and 36 that can be expanded and contracted with respect to the longitudinal direction of the connection device 20 are provided between the central portion 22a of the outer tube 22 of the connection device 20 and the tapered portions 27 and 28, respectively. It is provided. As shown by the dotted line in FIG. 3, when the inner tube 21 extends in the longitudinal direction larger than the outer tube 22, the bellows portions 35 and 36 are deformed so that the peaks are lowered and the central portion of the outer tube 22 is formed. Since the distance between 22a and each end 23 and 24 becomes long, the thermal stress between the inner tube 21 and the outer tube 22 is further relaxed. This embodiment is effective in relieving the thermal stress between the inner tube 21 and the outer tube 22 when the temperature of the high-temperature heat medium becomes higher than about 120 ° C. described above. In the present embodiment, it has been described that the bellows portions 35 and 36 are one mountain. However, the number of peaks may be two or more, and the bellows portions 35 and 36 are made of a thin metal material or a non-metal material. It may be configured to absorb a larger difference in thermal expansion.

  DESCRIPTION OF SYMBOLS 10 Solar collector, 11 Casing, 11a Wall, 12 Heater, 13 Heat collector, 14 Window glass, 15 Heater inlet pipe, 16 Heater outlet pipe, 18 Sunlight, 20 Connection apparatus, 21 Inner pipe, 22 Outer pipe , 22a Central part, 23, 31 Casing inner side end, 24, 32 Casing outer side end, 25 Low temperature heat medium outlet nozzle, 26 Low temperature heat medium inlet nozzle, 27, 28 Taper part, 29, 30 Straight part, 33 Heat medium Supply pipe, 34 Heat medium outlet pipe, 35, 36 bellows part, 41 reflector, 42 support member, 43 arm, 44 rotation axis, 50 position adjuster, 100 solar heat collection system.

Claims (3)

A casing,
A heater that is mounted in a casing and heats a heat medium flowing in the interior by heat from sunlight;
A connection device that is attached through the wall of the casing and distributes the low-temperature heat medium before being heated by the heater and the high-temperature heat medium after being heated by the heater between the inside and the outside of the casing; A solar collector comprising:
The connecting device is
An inner pipe through which a high-temperature heat medium flows;
An outer pipe whose outer surface is connected to the wall of the casing, and a low-temperature heat medium flows between the outer face of the inner pipe,
The outer pipe is connected to the outer surface of the inner pipe at the casing inner side end and the casing outer side end, respectively, and has a nozzle through which a low-temperature medium circulates on the inner side and the outer side of the casing,
Features a solar collector. A solar collector according to claim 1,
The outer diameter of the outer pipe gradually decreases toward the casing inner end and the outer casing end of the outer pipe,
The casing inner side end of the outer pipe and the casing outer side end of the outer pipe are connected so that the inner surface of the outer pipe is superimposed on the outer surface of the inner pipe,
Features a solar collector. A solar collector according to claim 1 or 2,
The outer tube includes an expansion / contraction portion that can be expanded and contracted in the longitudinal direction, either or both between the casing wall and the casing inner side end or between the casing wall and the casing outer side end,
Features a solar collector.

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