WO2012073664A1 - Solar thermal collector tube - Google Patents

Abstract

Disclosed is a solar thermal collector tube which increases heat collection efficiency by suppressing diffusion of energy transmitted to the heat medium circulating in an inner tube. A solar thermal collector tube (1) comprises an inner tube (11) which receives sunlight collected by a collector mechanism (2) and transmits the energy to a heat medium (14) circulating internally, and an outer tube (12) which forms a thermal insulation space (13) and covers the outer circumference of the inner tube (11). A solar thermal absorption film (11a) is applied to at least the part of the surface of the inner tube (11) that is irradiated by sunlight, and a heat reflective film (11b) is applied to the portion not irradiated with sunlight from the collector mechanism (2).

Description

Solar collector tube

The present invention relates to a solar heat collecting tube, and more particularly, an inner tube that receives sunlight collected by a light collecting mechanism and transmits energy to a heat medium that circulates inside, and an outer space of the outer periphery of the inner tube. The present invention relates to a solar heat collecting tube including an outer tube formed and covered.

Conventionally, sunlight collected by a trough reflector having a parabolic cross section is received, and an inner pipe that transmits energy to a heat medium that circulates in the interior and an outer periphery of the inner pipe are formed as a heat insulating space. A solar heat collecting tube composed of an outer tube that covers the surface is proposed (for example, see Patent Document 1).

By the way, the conventional solar heat collecting tube has been devised in various ways to increase the light collecting efficiency. For example, in the solar heat collecting tube described in Patent Document 1, a heat medium circulating inside is used. It has been proposed that an outer tube that covers the outer periphery of the inner tube that transmits energy by forming a heat insulating space is provided with a structural element that allows sunlight to converge on the inner tube.

JP 2004-239603 A

As described above, in the conventional solar heat collecting tube, in order to increase the heat collecting efficiency, most of the attention is paid to the sunlight collecting side such as a light collecting mechanism, and the inner tube in which the heat medium is circulated. In regard to, it is proposed to increase the heat collection efficiency by coloring the entire surface of the tube black, adding fine irregularities, or forming a surface antireflection layer or infrared reflection layer with a very special multilayer coating It was a grade.

In view of the actual situation of the above-described conventional solar heat collecting tube, the present invention can improve the heat collecting efficiency by suppressing the dissipation of energy transmitted to the heat medium flowing through the inner tube. It aims at providing a heat collecting tube.

Furthermore, the present invention provides a solar heat collecting tube capable of supporting a solar heat collecting tube while absorbing the thermal expansion (linear expansion) of the inner tube when connecting adjacent solar heat collecting tubes. The purpose is to provide.

Another object of the present invention is to provide a solar heat collecting tube that can reduce conduction heat transfer to a glass outer tube.

In order to achieve the above object, a solar heat collecting tube of the present invention receives sunlight collected by a light collecting mechanism and transmits energy to a heat medium that circulates inside, and an outer periphery of the inner tube. A solar heat collecting tube comprising an outer tube that forms a heat insulating space and covers the surface of the inner tube with a solar heat absorbing film on at least a portion irradiated with sunlight from the light collecting mechanism. It is characterized in that a heat reflecting film is applied to a portion not irradiated with sunlight from the optical mechanism.

In this case, a solar heat absorbing film is applied to the entire circumference of the surface of the inner tube, and a heat reflecting film is applied to a portion not irradiated with sunlight from the light collecting mechanism, or from the light collecting mechanism of the inner tube. It is possible to apply a solar heat absorbing film to a portion irradiated with sunlight, and to apply a heat reflecting film to a portion not irradiated with sunlight from the light collecting mechanism.

Further, the solar heat absorption film can be composed of a chromium oxide layer.

Further, the heat reflecting film can be composed of an aluminum foil or a thin plate.

Further, adjacent solar heat collecting tubes are coupled by forming a screw at a connecting portion of an inner tube of the solar heat collecting tube and connecting them in a non-stretched state by connecting members formed with screws at both ends, A support shaft protruding in the horizontal direction from the surface of the inner tube in the vicinity of the connected portion can be slidably inserted into a horizontal long hole formed in the solar heat collecting tube support member.

In addition, the solar heat collecting tube support member is composed of a grooved structure that blocks the sunlight irradiated from the condensing mechanism on the end of the outer tube that is fixed to the inner tube and has a space that allows ventilation. can do.

The condensing mechanism comprises a trough-type reflecting mirror having a parabolic cross section, the solar heat collecting tube support member is fixed to the reflecting mirror, and the reflecting mirror and the solar heat collecting tube are swung in common. The base can be swingably provided via a shaft.

According to the solar heat collecting tube of the present invention, a solar heat absorbing film is applied to at least a portion of the inner tube surface irradiated with sunlight from the light collecting mechanism, and at a portion not irradiated with sunlight from the light collecting mechanism. By applying the heat reflecting film, it is possible to increase the absorption of energy into the heat medium that circulates in the inner tube and to suppress the dissipation of the energy transmitted to the heat medium, thereby increasing the heat collection efficiency. Can do.

Further, by constituting the solar heat absorption film from the chromium oxide layer, the absorption of energy to the heat medium flowing through the inner tube can be enhanced with a relatively inexpensive structure.

Further, by constituting the heat reflecting film from an aluminum foil or a thin plate, it is possible to suppress the dissipation of energy transmitted to the heat medium flowing through the inside of the inner tube with a relatively inexpensive material.

Further, adjacent solar heat collecting tubes are coupled by forming a screw at a connecting portion of an inner tube of the solar heat collecting tube and connecting them in a non-stretched state by connecting members formed with screws at both ends, By slidably fitting a support shaft that protrudes in the horizontal direction from the surface of the inner tube near the connected location, into a horizontal long hole formed in the solar heat collecting tube support member, Adjacent solar heat collecting tubes are connected to each other in a simple and strong manner by screwing the inner tubes of the solar heat collecting tubes into a non-stretchable state with a connecting member, and the vicinity of the connected portion is connected to the solar heat collecting tube. The support member can be supported while absorbing the thermal expansion (linear expansion) of the inner tube.

Further, the solar heat collecting tube support member has a groove-like structure that blocks sunlight irradiated from the light collecting mechanism at the end of the outer tube that is fixed to the inner tube, and has a space that allows ventilation. Thus, the conduction heat transfer to the glass outer tube can be reduced.

The condensing mechanism comprises a trough-type reflecting mirror having a parabolic cross section, the solar heat collecting tube support member is fixed to the reflecting mirror, and the reflecting mirror and the solar heat collecting tube are swung in common. By providing the base so as to be swingable via the shaft, the reflecting mirror and the solar heat collecting tube can be configured as an integrally structured swinging body.

One Example of the solar heat collecting apparatus to which the solar heat collecting tube of this invention is applied is shown, (a) is a front view, (b) is side sectional drawing. The Example from which the solar heat collector which applied the solar heat collecting tube of this invention is shown is shown, (a) is a front view, (b) is a top view, (c) is side sectional drawing. One Example of the solar heat collecting tube of this invention is shown, (a) is the schematic of an external appearance, (b1) and (b2) are the schematic of a cross section, (c) is explanatory drawing of a use condition. It is explanatory drawing which shows the connection and support structure of a solar heat collecting tube. It is explanatory drawing of a solar heat collecting tube, (a) is front sectional drawing, (b) is XX end elevation of (a), (c) is YY and ZZ end elevation of (a). .

Hereinafter, embodiments of the solar heat collecting tube of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of a solar heat collecting apparatus to which the solar heat collecting tube of the present invention is applied.
This solar heat collecting device receives sunlight collected by a trough reflector 2 having a parabolic cross section as a condensing mechanism, and transmits energy to a heat medium 14 that circulates inside the solar heat collecting device. 11 and a solar heat collecting tube 1 including an outer tube 12 that covers the outer periphery of the inner tube 11 by forming a heat insulating space 13.

In this case, the solar heat collecting tube 1 and the reflecting mirror 2 are arranged on the base 3 such that the central axis L1 of the solar heat collecting tube 1 and the reflecting mirror 2 is along the north-south axis, and the solar heat collecting tube 1 and the reflecting mirror 2 The mirror 2 is installed so as to be swingable through a common swing shaft 4.
And the solar tracking mechanism 5 which rotates the rocking | fluctuation axis | shaft 4 according to a solar motion so that the extension direction of the surface containing the bisector L2 of the solar heat collecting tube 1 and the reflective mirror 2 may always point to the direction of the sun. To be provided.

As a result, the sunlight Sb is always incident on the reflecting mirror 2 in parallel with the plane including the bisector L2 of the reflecting mirror 2, and the reflected light is installed at the focal point of the reflecting mirror 2. 1 is focused on the central axis L1.

In this embodiment, the reflecting mirror 2 is a frame made of an aluminum extrusion-molded material in which an aluminum plate serving as a supporting material and a high-reflectance aluminum plate serving as a mirror are overlapped. Although it is configured to be fitted into a member, a glass mirror made of a thin plate that can be bent can also be used.

In the present embodiment, the trough-type reflecting mirror 2 having a parabolic cross section is used as a condensing mechanism, but in addition to a Fresnel mirror-type reflecting mirror composed of a plurality of long planar split mirrors, A known condensing mechanism such as a linear Fresnel lens 6 as shown in FIG. 2 can be used.

By the way, in the present embodiment, the solar heat collecting tube 1 receives sunlight collected by the reflecting mirror 2 as a condensing mechanism as shown in FIG. The sunlight from at least the reflecting mirror 2 on the surface of the inner tube 11 of the solar heat collecting tube 1 is composed of an inner tube 11 that transmits the outer tube 12 and an outer tube 12 that covers the outer periphery of the inner tube 11 by forming a heat insulating space 13. The solar heat absorption film 11a is applied to the irradiated portion (the portion irradiated with the reflected light of the sunlight Sb on the reflecting mirror 2 side), and the portion not irradiated with the sunlight from the reflecting mirror 2 (opposite of the reflecting mirror 2) The portion where the reflected light of the side sunlight Sb is not irradiated) is provided with a heat reflecting film 11b.

More specifically, at least a portion of the surface of the inner tube 11 irradiated with sunlight from the reflecting mirror 2 (in this embodiment, the entire circumference of the surface of the inner tube 11 (FIG. 3 (b1)) or the lower side. In the 180 ° range (FIG. 3 (b2)), a chromium oxide plating layer is applied as the solar heat absorbing film 11a.
Note that the solar heat absorption film 11a can be formed only on the portion irradiated with sunlight from the reflecting mirror 2.
And the chromium oxide plating layer as the solar heat absorption film 11a can be formed at a relatively low cost by performing a chromium oxide plating process on the surface of the inner tube 11 made of a pickled steel pipe.
In addition, the material and formation method of the solar heat absorption film 11a are not limited to this, As a material, in addition to chromium oxide, a nickel-based material or the like is used. In order to enhance the absorption of solar heat by physical vapor deposition (PVD), coating, etc., conventionally known ones can be employed such as coloring the surface black or applying an appropriate selective absorption film.

Further, a portion not irradiated with sunlight from the reflecting mirror 2 (in this embodiment, a range of 180 ° above the surface of the solar heat absorption film 11a formed on the entire circumference of the surface of the inner tube 11 (FIG. 3 (b1 )) Or a range of 180 ° above the surface of the inner tube 11 (FIG. 3 (b2))), an aluminum foil or a thin plate is applied as the heat reflecting film 11b.
In addition, the heat | fever reflective film | membrane 11b can also be formed in the whole part which the sunlight from the reflective mirror 2 is not irradiated.
The aluminum foil or thin plate as the heat reflecting film 11b can be formed at a relatively low cost by bonding with an adhesive such as a silicon resin.
In this case, by bonding aluminum foil or thin plate through an adhesive such as silicon resin, in addition to the heat reflection function, the heat insulating function of the adhesive is added (the heat insulating function is further improved by foaming the adhesive) The energy transmitted to the heat medium 14 can be confined in the inner tube 11 and energy dissipation can be suppressed.
The material and the formation method of the heat reflecting film 11b are not limited to this, and a white or silver heat-resistant heat-insulating paint having a heat reflecting function (a function of enclosing the energy transmitted to the heat medium 14 in the inner tube 11). For example, conventionally known materials such as a ceramic-based adhesive or silicon resin as a binder containing a fine hollow ceramic, a heat insulating sheet material made of glass wool or the like can be used. It is also possible to physically fix the aluminum thin plate with a band or the like.

Note that a metal tube such as a stainless steel tube can be suitably used for the inner tube 11 and a borosilicate glass tube such as a Kovar glass tube can be suitably used for the outer tube 12.

In addition, the heat insulating space 13 is normally insulated by making a vacuum between the inner tube 11 and the outer tube 12.

The heat medium 14 that circulates in the inner tube 11 is heated to a temperature of several hundred degrees C., for example, about 400 degrees C., and functions as a heat medium such as water, heat medium oil, or molten salt. Can be used.

The solar heat collecting tube 1 applies a solar heat absorption film 11a to at least a portion of the surface of the inner tube 11 irradiated with sunlight from the reflecting mirror 2 as a condensing mechanism, and the sunlight from the reflecting mirror 2 By applying the heat reflecting film 11b to the unirradiated portion, the solar heat absorbing film 11a increases the absorption of energy into the heat medium 14 flowing through the inner tube 11, and the heat reflecting film 11b applies the heat reflecting film 11b to the heat medium 14. The transmitted energy is confined in the inner tube 11 and energy dissipation can be suppressed, thereby improving the heat collection efficiency.

Hereinafter, the performance of the solar heat collecting tube will be verified.
[Case 1]
・ Heating medium heating temperature: 400 ° C
・ Reflector width 2m, length 5m
When a solar heat absorption film (chromium oxide plating layer) is applied to the entire surface of the inner tube σx (273 + 400) ⁴ = 11632 W / m ²
σ (Stephan Boltzmann coefficient) = 5.67 × 10 ⁻⁸ W / (m ² · K ⁴ )
Emissivity: ε = 0.6, inner tube surface area: 0.534 m ² ,
Heat dissipation: 0.6 × 11632 × 0.534 = 3.73 kW (1)
・ When a solar heat absorption film (chromium oxide plating layer) is applied to the entire surface of the inner tube, and a heat reflection film (aluminum foil) is applied to the half of the surface, the emissivity of the aluminum foil: ε = 0.1 Solar heat absorption film Heat dissipation from the (chrome oxide plating layer) part: 1.86 kW
Heat dissipation from heat reflecting film (aluminum foil) part: 0.31kW
Total heat dissipation: 2.27kW (2)
・ The amount of heat absorbed by the solar heat collection tube when the direct solar radiation from the sun is 1 kW / m ²・ When the solar heat absorption film (chromium oxide plating layer) is applied to the entire surface of the inner tube The opposite side of the reflector: 10 × 25/1000 × 0.9 × 0.95 = 0.11
Reflector side: 10 × 1975/2000 × 0.9 × 0.9 × 0.95 = 7.60
Total heat quantity: 7.71 kW (3)
・ When a solar heat absorption film (chromium oxide plating layer) is applied to the entire surface of the inner tube, and a heat reflection film (aluminum foil) is applied to half of the surface, the opposite side of the reflector: 10 x 25/1000 x 0.9 x 0 = 0
Reflector side: 10 × 1975/2000 × 0.9 × 0.9 × 0.95 = 7.60
Total heat: 7.60 kW (4)
-Thermal efficiency-When a solar heat absorption film (chromium oxide plating layer) is applied to the entire surface of the inner tube (3)-(1) = 3.98 kW → Thermal efficiency: 3.98 kW / 10 kW = 39.8%
・ When a solar heat absorption film (chromium oxide plating layer) is applied to the entire surface of the inner tube, and a heat reflection film (aluminum foil) is applied to half of the surface (4)-(2) = 5.43 kW → thermal efficiency: 5. 43kW / 10kW = 54.3%

[Case 2]
・ Heating medium heating temperature: 200 ° C
・ Reflector width 2m, length 5m
When a solar heat absorption film (chromium oxide plating layer) is applied to the entire surface of the inner tube σx (273 + 200) ⁴ = 2838 W / m ²
σ (Stephan Boltzmann coefficient) = 5.67 × 10 ⁻⁸ W / (m ² · K ⁴ )
Emissivity: ε = 0.6, inner tube surface area: 0.534 m ² ,
Heat dissipation: 0.6 x 2838 x 0.534 = 0.91 kW (5)
・ When a solar heat absorption film (chromium oxide plating layer) is applied to the entire surface of the inner tube, and a heat reflection film (aluminum foil) is applied to the half of the surface, the emissivity of the aluminum foil: ε = 0.1 Solar heat absorption film Heat dissipation from the (chrome oxide plating layer) part: 0.46 kW
Heat dissipation from heat reflecting film (aluminum foil) part: 0.08kW
Total heat dissipation: 0.54kW (6)
・ The amount of heat absorbed by the solar heat collection tube when the direct solar radiation from the sun is 1 kW / m ²・ When the solar heat absorption film (chrome oxide plating layer) is applied to the entire surface of the inner tube The opposite side of the reflector: 10 × 25/1000 × 0.9 × 0.95 = 0.11
Reflector side: 10 × 1975/2000 × 0.9 × 0.9 × 0.95 = 7.60
Total heat quantity: 7.71 kW (7)
・ When a solar heat absorption film (chromium oxide plating layer) is applied to the entire surface of the inner tube, and a heat reflection film (aluminum foil) is applied to half of the surface, the other side of the reflector: 10 x 25/1000 x 0.9 x 0 = 0
Reflector side: 10 × 1975/2000 × 0.9 × 0.9 × 0.95 = 7.60
Total heat: 7.60 kW (8)
・ Thermal efficiency ・ When a solar heat absorption film (chromium oxide plating layer) is applied to the entire surface of the inner tube (7) − (5) = 6.80 kW → Thermal efficiency: 6.80 kW / 10 kW = 68.0%
・ When a solar heat absorption film (chromium oxide plating layer) is applied to the entire surface of the inner tube, and a heat reflection film (aluminum foil) is applied to half of the surface (8)-(6) = 7.06 kW → thermal efficiency: 7. 06kW / 10kW = 70.6%

From the verification results of the performance of the solar heat collecting tube described above, by applying the heat reflecting film 11b to the portion not irradiated with sunlight from the reflecting mirror 2, the energy transmitted to the heat medium 14 is enclosed in the inner tube 11, It has been confirmed that energy dissipation can be suppressed, thereby improving the heat collection efficiency, and particularly when the heating temperature of the heat medium is high.

Further, as shown in FIGS. 4 and 5, thermal expansion (line) of the inner tube 11 and the outer tube 12 including the metal ring 25 a and the bellows 25 b in which both ends of the inner tube 11 are joined to the end of the outer tube 12. It is fixed through an expansion difference absorbing mechanism 25 that absorbs the difference in expansion.

Then, the adjacent solar heat collecting tubes 1 configured as described above are non-stretched by the connecting member 23 in which a screw is formed on the connecting portion 11c of the inner tube 11 of the solar heat collecting tube 1 and the screws are formed at both ends. The support shaft 24 that is connected by connecting to the state and projecting horizontally from the surface of the inner tube 11 in the vicinity of the connected portion is formed on the solar heat collecting tube support members 3a1 to 3a4 and 3b1 to 3b3. It is slidably inserted into the horizontal long hole 31.
In this case, by continuously forming a notch portion 32 that opens upward at one end side or in the vicinity of one end side of the long hole 31, the insertion of the support shaft 24 into the long hole 31 is made via the notch portion 32. Can be done smoothly.

As a result, the adjacent solar heat collecting tubes 1 are connected to each other easily and firmly by screw-connecting the inner tubes 11 of the solar heat collecting tubes 1 to each other in a non-stretchable state by the connecting member 23. The vicinity can be supported by the solar heat collecting tube support members 3a1 to 3a4 and 3b1 to 3b3 while absorbing the thermal expansion (linear expansion) of the inner tube 11.

In addition, the edge part which is not connected with the solar heat collecting tube 1 of the solar heat collecting tube 1 connected in this way is comprised as a free end, for example, connects the flexible tube 26 to the inner tube 11 of the solar heat collecting tube 1. Thereby, the thermal expansion (linear expansion) of the inner tube 11 can be absorbed.

In this embodiment, the solar heat collecting tube support members 3a1 to 3a4 and 3b1 to 3b3 are fixed to the trough type reflecting mirror 2 having a parabolic cross section as the light collecting mechanism. By providing the heat collecting tube 1 on the base 3 through a common rocking shaft 4 so as to be rockable, the reflecting mirror 2 and the solar heat collecting tube 1 are configured as an integral rocking body.

The solar heat collecting tube support members 3a1 to 3a4 and 3b1 to 3b3 have a function of supporting the solar heat collecting tube 1, specifically, the inner tube 11 while absorbing the thermal expansion (linear expansion). Reflecting mirror as a condensing mechanism in the end of the outer tube 12 fixed to the tube 11, specifically, the expansion difference absorption mechanism 25 composed of a metal ring 25 a and a bellows 25 b joined to the end of the outer tube 12. In addition to blocking sunlight radiated from 2, an upwardly opening groove-like structure is provided with a ventable space for enabling heat dissipation by external air convection.
Thereby, the conduction heat transfer to the outer tube | pipe 12 through the expansion difference absorption mechanism 25 which consists of the metal ring 25a and the bellows 25b joined to the edge part of the outer tube | pipe 12 can be made small.

As described above, the solar heat collecting tube of the present invention has been described based on the embodiments thereof, but the present invention is not limited to the configurations described in the above embodiments, and the configurations thereof are appropriately set within the scope not departing from the gist thereof. It can be changed.

The solar heat collecting tube of the present invention has a characteristic that can improve the heat collecting efficiency by suppressing the dissipation of energy transmitted to the heat medium flowing through the inside of the inner tube. It can use suitably for the use of the solar heat collecting device which uses a heat tube.

DESCRIPTION OF SYMBOLS 1 Solar collector tube 11 Inner tube 11a Solar heat absorption film 11b Heat reflection film 11c Connection part 12 Outer tube 13 Thermal insulation space 14 Heat medium 2 Reflecting mirror (condensing mechanism)
6 Linear Fresnel lens (light collecting mechanism)
24 Support shaft 25 Expansion difference absorbing mechanism 25a Metal ring 25b Bellows 3a1-3a4, 3b1-3b3 Solar heat collecting tube support member 31 Long hole 32 Notch Sb Sunlight

Claims (8)

A solar light collection comprising an inner tube that receives sunlight collected by the light collecting mechanism and transmits energy to a heat medium that circulates inside, and an outer tube that covers the outer periphery of the inner tube by forming a heat insulating space. In the heat tube, a solar heat absorption film is applied to at least a portion of the surface of the inner tube that is irradiated with sunlight from the light collecting mechanism, and a heat reflecting film is applied to a portion that is not irradiated with sunlight from the light collecting mechanism. A solar heat collecting tube characterized by The solar heat collecting tube according to claim 1, wherein a solar heat absorption film is applied to the entire circumference of the surface of the inner tube, and a heat reflecting film is applied to a portion not irradiated with sunlight from the light collecting mechanism. . A solar heat absorption film is applied to a portion of the inner tube that is irradiated with sunlight from the light collecting mechanism, and a heat reflective film is applied to a portion that is not irradiated with sunlight from the light collecting mechanism. The solar heat collecting tube according to claim 1. The solar heat collecting tube according to claim 1, 2 or 3, wherein the solar heat absorption film is made of a chromium oxide layer. The solar heat collecting tube according to claim 1, 2, 3, or 4, wherein the heat reflecting film is made of an aluminum foil or a thin plate. Adjacent solar heat collecting tubes are connected to each other by forming a screw at a connecting portion of the inner tube of the solar heat collecting tube and connecting them in a non-stretchable state by connecting members formed with screws at both ends. 2. A support shaft projecting in a horizontal direction from the surface of the inner pipe in the vicinity of the portion is slidably fitted into a horizontal slot formed in a solar heat collecting tube support member. The solar heat collecting tube of 2, 3, 4, or 5. The solar heat collecting tube support member has a groove-like structure with a space that allows ventilation while blocking the sunlight irradiated from the condensing mechanism on the end of the outer tube that is fixed to the inner tube. The solar heat collecting tube according to claim 6, wherein the solar heat collecting tube is characterized in that: The condensing mechanism comprises a trough-type reflecting mirror having a parabolic cross section, the solar heat collecting tube support member is fixed to the reflecting mirror, and the reflecting mirror and the solar heat collecting tube have a common swing axis. The solar heat collecting tube according to claim 6 or 7, wherein the solar heat collecting tube is swingably provided on the base.

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