JP2005214604A - Vacuum flat-plate type solar heat collector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an efficient vacuum flat-plate type solar heat collector by reducing heat loss due to escape of secondary radiation from a back side of a heat collecting plate to an outside through a space between the heat collecting plate and a column and the space between the heat collecting plate and a casing. <P>SOLUTION: Even when the heat collecting plate 4 is expanded due to heat and a hole 11 of the heat collecting plate 4 is moved, a first barrier material 14 formed of a metal plate or a plate type heat insulating material with the size permitting blocking the space 12 between the heat collecting plate 4 and the column 8 is placed on the heat collecting plate 4 for blocking the space between the heat collecting plate 4 and the column 8, and a second barrier material 15 formed of a metal plate or a plate type heat insulating material having the outer circumference with size permitting contacting the inner circumference of the casing 2 and a hole with a smaller inner circumference than the outer circumference of the heat collecting plate 4 is placed on the heat collecting plate 4 for blocking the space 13 between the heat collecting plate 4 and the casing 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vacuum flat plate solar collector, and more particularly to a technique for reducing the radiation loss.

Conventionally, as shown in Patent Document 1, a vacuum flat plate solar collector has been proposed by the present inventors. In this vacuum flat plate solar heat collecting apparatus, the inside of the casing is evacuated and a reflective film is formed on the back surface of the heat collecting plate to reduce heat loss from the back surface of the heat collecting plate.
On the other hand, Non-Patent Document 1 describes cavity radiation.
Japanese Patent Laid-Open No. 11-14162 Title: Introduction to Heat Transfer, Author: Yoshiro Kato, Publication: Yokendo Co., Ltd. July 20, 1990 29th Edition 385-386

  However, in the case of a high vacuum type, the high vacuum itself has a high thermal insulation property against conduction heat transfer, so the following problems peculiar to high vacuum occur. It becomes a problem to do.

In the vacuum solar heat collector, a large number of pillars are set up to disperse and receive the atmospheric pressure applied to the window glass, but when the temperature of the heat collecting plate rises, the difference in expansion from the housing that does not rise in temperature There is a possibility that a dimensional difference occurs and the pillar and the heat collecting plate come into contact with each other. When the pillar and the heat collecting plate come into contact with each other, there is a risk that the heat escapes from the heat transfer and the efficiency of the solar heat collecting device decreases, or the pillar or the heat collecting plate is destroyed.
The same is true between the housing and the heat collecting plate. When the temperature of the heat collecting plate rises and expands, there is a possibility that the heat collecting plate touches the inner periphery of the housing.

Therefore, even if the heat collecting plate expands due to a temperature rise, the heat collecting plate does not come into contact with the inner periphery of the pillar or the housing, so that the space between the pillar supporting the window glass and the heat collecting plate and the housing and the heat collecting plate are not. There must be enough space between them.
However, if so, a loss due to radiant heat transfer, so-called radiation leakage occurs, in the form of infrared radiation of secondary radiation generated from the back surface of the heated heat collecting plate radiating to the outside through the gap. Similarly, loss due to radiation leakage occurs from the gap between the heat collecting plate and the housing.

  This radiation leakage is caused by radiation in the form of so-called cavity radiation because the area of the gap is much smaller than the area of the back surface of the heat collecting plate. Radiation leakage occurs.

  In order to reduce the radiation loss that the infrared radiation of the secondary radiation radiated from the warmed heat collecting plate leaks outside through the gap formed between the heat collecting plate and the column and between the heat collecting plate and the housing, The present invention relates to a vacuum flat plate solar heat collecting apparatus, wherein a first blocking material is placed on a heat collecting plate to close a gap between the heat collecting plate and a column, and a second blocking material is placed on the heat collecting plate. Alternatively, the gap between the heat collecting plate and the housing is closed by supporting from below.

For example, as a means for blocking infrared rays passing through the gap between the pillar and the heat collecting plate, it has a hole that is large enough to close the gap and has a slightly larger diameter that is almost the same as a metal pillar. A first blocking material made of a plate-like member is passed through the column, and the first blocking material is in contact with the heat collecting plate at the gap between the column and the heat collecting plate to close the gap.
In order to make the first blocking material contact the heat collecting plate, the first blocking material is placed on the heat collecting plate so that the first blocking material contacts the heat collecting plate by gravity. Further, the first blocking member may be pushed down by a spring so as to contact the heat collecting plate.
The gap formed between the outer peripheral edge of the heat collecting plate and the vertical wall of the housing also has, for example, an outer periphery of a size that is in contact with the inner periphery of the housing, that is, an outer periphery that is substantially the same as the inner periphery. A second blocking material made of a plate-like member having a small inner peripheral hole is used to close the gap so as to be in contact with the heat collecting plate at the gap between the heat collecting plate and the housing.
In order to come into contact with the heat collecting plate, for example, a second blocking material is placed on top of the heat collecting plate so that the second blocking material comes into contact with the heat collecting plate by gravity. Further, the second blocking material may be pushed down by a spring so as to contact the heat collecting plate.

The plate-like member is a metal thin plate that reflects infrared rays, or a thin plate that uses a material that absorbs infrared rays and is a thermal insulator such as glass, ceramics, ceramics, and plastics that has a small amount of adsorbed gas.
When a material with high infrared emissivity, such as glass, is used for the member that blocks infrared rays that pass through the gap, a metal film with low infrared emissivity is placed on the surface of the blocking material to further reduce radiation loss. It is formed using techniques such as vapor deposition and plating.
When a member with a large amount of adsorbed gas such as plastic is used, the metal is attached to the surface slightly thicker to prevent the adsorbed gas from being released.

  Still another means is that the first blocking material is as described above, but the second blocking material is a thermal insulator made of a material having a low thermal conductivity such as glass or ceramics, which is installed on the inner periphery of the casing. A frame shape, for example, a cylindrical shape when the device is circular, a square tube shape when the device is square, and a means for placing and supporting the peripheral portion of the heat collecting plate on the second blocking material Take the gap between the heat collecting plate and the housing from the bottom. A metal thin film is attached to the surface of the second blocking material so as to reflect infrared rays.

In addition, in order to prevent radiation loss radiated and lost from the back surface of the heat collecting plate to the bottom of the housing, a metal thin film is attached to the back surface of the heat collecting plate and the bottom of the housing facing it by vacuum deposition. Use high reflectivity (low emissivity) in the infrared region to reduce radiation loss.
In order to prevent the adsorbed gas from the glass and the housing from seeping out for a long time and breaking the vacuum inside the housing, it is necessary to adsorb these gases and maintain the vacuum for many years. A getter material that adsorbs gas is attached to the back surface and the bottom of the opposite housing.
To prevent radiation loss that is lost by radiating from the back of the heat collecting plate to the bottom of the housing and to prevent the vacuum inside the housing from being broken by the adsorbed gas that exudes from the window glass and the housing. Using a metal material having a low infrared emissivity and a getter action, such as aluminum, an aluminum thin film is formed by vacuum deposition on the back surface and the bottom of the housing, and the aluminum thin film has a high in the infrared region. Reflectance is used to reduce radiation loss and to absorb the gas that oozes out of the window glass or housing.

  According to the present invention, the heat insulation of the heat collecting plate of the vacuum plate type solar heat collecting device becomes very good by closing the gap between the heat collecting plate and the pillar, and the heat collecting plate and the housing, and the heat loss is extremely Because it is less, solar heat can be efficiently used in a wide range from the cold zone to the tropics, and it can be used efficiently in a wide range of fields, from home use to industrial use and agricultural use. A large amount of heat can be obtained without generating energy, making a great contribution both in terms of energy supply and environmental improvement, and its utility is enormous.

  A window glass, a housing, a plurality of pillars for supporting atmospheric pressure between the window glass and the bottom of the housing, and a hole having a size through which the pillars penetrate and do not come into contact, are arranged in the housing. In a vacuum flat plate solar collector equipped with a heat plate, a column is inserted and has a hole that is slightly larger than the outer periphery of the column. Passing the first shielding material formed of a metal plate or a plate-like thermal insulator having a size capable of closing the gap between the hot plate and the column through the column and on the heat collecting plate, It is a metal plate or plate-shaped thermal insulator that closes the gap between the heat collecting plate and the pillar, has an outer periphery that is in contact with the inner periphery of the housing, and has an inner peripheral hole smaller than the outer periphery of the heat collecting plate. This can be realized by placing the formed second blocking material on the heat collecting plate and closing the gap between the heat collecting plate and the housing.

1A and 1B show a first embodiment of the present invention, in which FIG. 1A is a cross-sectional plan view with a column portion taken as a cross section, and FIG.
In FIG. 1, 1 is a vacuum flat plate solar collector, 2 is a housing, 3 is a window glass supported on the top of a housing 2, 4 is a heat collecting plate supported by a pillar not shown, and 5 is a heat collecting plate. Pipe, 6 is an input terminal of the inlet of the heat medium, 7 is an output terminal of the outlet of the heat, 8 is a column supporting the window glass 3, 9 is a tube inserted outside the central column 8, and 10 is outside the tube 9 A pipe to be inserted, 11 is a hole through which the pillar 8 opened in the heat collecting plate 4 is passed, 12 is a gap formed between the pillar 8 and the heat collecting plate 4 in the hole 11 portion, and 13 is a peripheral edge of the heat collecting plate 4 A gap formed between the vertical wall of the housing 2, 14 is a first blocking material for closing the gap 12, and 15 is a second blocking material for closing the gap 13.

The vacuum flat plate solar heat collecting apparatus 1 keeps the inside of the housing 2 at a high vacuum of about 0.1 Pascal or less. At such a high vacuum, heat conduction occurs under free molecular conditions, and the flow of thermal energy is proportional to the pressure and temperature difference and is not related to the distance between the two surfaces. Regardless of the thickness, good thermal insulation can be obtained. Therefore, in such an environment, it is relatively easy to prevent heat loss from the heat collecting plate 4 due to heat conduction, and the heat collecting plate 4 is directly a good conductor of heat such as the housing 2 or the column 8. Do not touch the
For this purpose, the holes 11 through which the metal pillars 8 supporting the window glass 3 penetrate the heat collecting plates 4 are devised so that the heat collecting plates 4 do not contact the metal pillars 8 as much as possible. For example, the diameter of the hole 11 is set larger than the diameter of the column 8. Thus, heat loss due to heat conduction can be prevented.

  The most important thing to note when opening the holes 11 is that the heat collecting plate 4 expands when the temperature of the heat collecting plate 4 rises due to solar heat. The temperature of the heat collecting plate 4 of the high-vacuum solar heat collecting device is about 400 ° C. when it becomes empty for some reason, while the housing 2 is kept at a temperature close to the ambient temperature. 4 causes a considerable dimensional difference of several mm or more between the two. This expansion prevents destruction of the device. Therefore, both the gap 12 and the gap 13 have a size of several mm or more.

A reasonable method for reducing the influence of thermal expansion is to fix a hole located at the center of the heat collecting plate 4 at the center of the casing. In other words, the central hole of the heat collecting plate 4 is circular and no play is provided between the column 8 and the column 8. In this case, a tube made of a material having low thermal conductivity, for example, glass tubes 9 and 10 is inserted into the gap between the column 8 and the central hole 11 so that the column 8 and the heat collecting plate 4 are not in direct contact with each other. To do.
When the fixing hole is provided in the center of the heat collecting plate 4 as described above, the size of the gap 12 formed between the column 8 and the hole 11 due to the temperature rise of the heat collecting plate 4 is expanded due to the temperature rise of the heat collecting plate 4. Half of the amount.
When the central column 8 is made of a material having a low thermal conductivity, for example, glass, the glass tubes 9 and 10 are unnecessary and the column 8 and the heat collecting plate 4 are brought into contact with each other. Even when the column 8 is made of metal, if the central hole 11 of the heat collecting plate 4 is slightly larger than the column 8, for example, about 0.1 mm, it is thermally insulated. There is no need for the first blocking material 14 for the central hole 11.

Further, the heat collecting plate 4 is not rotated using one of the holes 11 in the periphery so that the heat collecting plate 4 rotates around the circular hole in the center and does not contact the metal pillar 8. To. The peripheral hole 11 is an elliptical hole, and the glass tube 9 is inserted in the gap between the hole and the column 8 so that the play in the circumferential direction does not occur.
As shown in FIG. 1 (a), the central hole 11 is circular, but gradually deforms from the center to an elliptical shape as it goes to the periphery. FIG. 1A shows the interrelationship between the pillar 8 and the hole 11 at room temperature.
The reason why it becomes elliptical as it goes to the periphery is that the central hole 11 is fixed to the column 8 and the rotational motion is suppressed, so that expansion occurs radially.

If the hole 11 is opened with the above consideration, the heat collecting plate 4 will not contact the column 8 or the housing 2 due to thermal expansion, and heat loss will not occur due to heat conduction. By doing so, a gap 12 is formed between the heat collecting plate 4 and the column 8, and a gap 13 is formed between the heat collecting plate 4 and the housing 2.
If it does so, the infrared rays of the secondary radiation from the back of the heat collecting plate 4 will leak to the upper part of the heat collecting plate 4 through the clearance gap 12 and the clearance gap 13, and will be absorbed by the window glass 3, and will cause a radiation loss.
Since the area of the back surface of the heat collecting plate 4 is far larger than the total area of the gap 12 and the gap 13, the radiation leaking from the gap 12 and the gap 13 becomes so-called cavity radiation, and the radiation of the gap 12 and the like. The rate is much higher than the emissivity from the back side of the heat collecting plate 4 and approaches the emissivity of the black body. Therefore, even if the areas of the gap 12 and the gap 13 are small, the amount of infrared rays leaking to the outside through the gap 12 and the gap 13 is large, which is a value that cannot be ignored for a high-vacuum solar heat collector for the purpose of low loss. .

Therefore, in order to reduce the radiation leakage and make a highly efficient solar heat collecting device, it is very important to close the gap 12 and the gap 13 with a blocking material made of a material that does not transmit infrared rays. In addition, it is necessary to close the gap with a blocking material that does not cause or hardly causes a heat transfer loss.
The means for blocking infrared rays passing through the gap 12 between the column 8 and the heat collecting plate 2 is substantially the same as the column 8 so as to be large enough to block the gap 12 and to allow the column 8 to be inserted. The plate-shaped first blocking member 14 having a slightly larger hole is passed through the column 8 and placed on the heat collecting plate 4 so that the first blocking member 14 contacts the heat collecting plate 4 by gravity. To close the gap 12.
When the column 8 is a cylinder, the hole is also circular, and when the column 8 has a diameter of, for example, 3.0 mm, the diameter of the hole is preferably about 31 mm.

FIG. 2 is a view for explaining the size of the first blocking material.
The first blocking member 14 is fixed at a relative position to the housing 2 by the pillar 8.
Therefore, when the heat collecting plate 4 is thermally expanded, the outermost hole 11 provided in the heat collecting plate 4 moves from the solid line to the broken line, or from the broken line to the solid line, and changes the relative position with the housing 2.
Therefore, the blocking material 14 is displaced while being in contact with the heat collecting plate 4, and the relative position with the gap 12 is also changed. Thus, even if the gap 12 changes its position due to the thermal expansion of the heat collecting plate 4, the first blocking member 14 needs to have a size that can completely block the gap 12.
As a result, even if the temperature of the heat collecting plate 4 fluctuates and the position of the gap 12 fluctuates, the gap 12 is always covered with the first blocking member 14 and the infrared radiation of the secondary radiation is transmitted from the gap 12 to the outside. There is no leakage.
Although the shape is circular, the shape is not particularly limited as long as it is large enough to close the gap 12.

The gap 13 formed between the outer peripheral edge of the heat collecting plate 4 and the housing 2 also has an outer periphery that is substantially the same as the inner periphery of the housing 2, and has an inner peripheral hole that is, for example, several mm or more smaller than the outer periphery of the heat collecting plate 4. A plate-shaped second blocking material 15 having the heat sink 4 is placed on the heat collecting plate 4 to close the gap 13 between the heat collecting plate 4 and the housing 2.
Since the second blocking material 15 is formed to have an inner circumference smaller than the outer circumference of the heat collecting plate 4, the second blocking material 15 is not attached to the heat collecting plate 4 even if the heat collecting plate 4 is deformed by heat. While sliding, the gap 13 is always closed.
As described above, when the first and second blocking members 14 and 15 are placed on the heat collecting plate 4, the first and second blocking members 14 and 15 come into contact with the heat collecting plate 4 by their own weight. The gaps 12 and 13 can be closed. At this time, the first and second blocking members 14 and 15 may be pressed against the heat collecting plate 4 from above by a spring.

  The reason why the inner periphery of the first blocking member 14 is slightly larger than the outer periphery of the column 8 is that the first blocking member 14 is in close contact with the column 8 and heat conduction therebetween is improved, so that the solar heat is the first. This is because a small gap is made between them so as to prevent the loss from flowing through the pillars 8 to the pillars 8 through the blocking material 14. As described above, since the inside of the housing 2 has a high degree of vacuum so as to achieve heat conduction under free molecular conditions, the flow of heat can be interrupted even with a slight gap of about 0.1 mm. Take the method.

The plate-like members of the first and second blocking members 14 and 15 are thin metal plates that reflect infrared rays, or heat insulators such as glass, ceramics, and ceramics that absorb infrared rays, and have a small amount of adsorbed gas. Use materials.
Specific examples of the first and second blocking materials 14 and 15 include a thin plate made of a metal material having a low thermal conductivity such as stainless steel and having a thickness of about 0.3 mm or less, or a metal thin film formed on the surface. And a plate with a thickness of several millimeters made of a heat insulating material such as glass or ceramic. Further, a thin plate or the like in which a metal thin film is attached to the surface of a plastic thin plate that can withstand high heat, such as polyimide, in order to improve the reflection of infrared rays and suppress the release of adsorbed gas may be used.

A selective absorption film is formed on the top surfaces of the first and second blocking materials 14 and 15. A selective absorption film is a film that absorbs solar heat and suppresses far-infrared radiation, and is formed of a multilayer film of gold, silver, etc. by applying chromium, titanium oxide, metal deposition, electrolysis, etc. Is formed on the surface.
When this selective absorption film is formed on the upper surface, the upper surfaces of the first and second blocking members 14 and 15 also receive solar heat and the temperature rises, and the lower surface also comes into contact with the heat collecting plate 4 to increase the temperature. Therefore, there is an effect that heat does not escape upward.
In addition, when the 1st and 2nd shielding materials 14 and 15 are formed with a heat insulator, the selective absorption film is further formed on the metal thin film formed on the heat insulator.

As described above, according to the first embodiment, the gaps 12 between the heat collecting plate 4 and the column 8 and the gaps 13 between the heat collecting plate 4 and the housing 2 are formed by the first and second blocking members 14 and 15. If the leakage of infrared rays is prevented by blocking, in the experiment, the saturation temperature of the heat collecting plate 4 is increased by about 25 to 30% at a vacuum degree of about 0.01 Pascal when there is solar heat input.
Further, if a selective absorption film is formed on the upper surfaces of the first and second blocking members 14 and 15, heat does not escape upward, and as a result, heat radiation leakage can be reduced.

FIG. 3 is a sectional side view of the main part showing Embodiment 2 of the present invention.
In the second embodiment, a vertical portion 22 is formed in the peripheral portion of the second blocking member 21, and a plurality of portions of the vertical portion 22 are fixed to the vertical wall 23 of the housing 2 by brazing or the like. The rest of the configuration is the same as in the first embodiment, including closing the gap 13 between the heat collecting plate 4 and the housing 2 by the second blocking material 21.
According to the second embodiment, in addition to the effects of the first embodiment, the second blocking material 21 is fixed to the housing 2, so that the position of the second blocking material 21 is determined.

FIG. 4 is a side cross-sectional view of a main part showing Embodiment 3 of the present invention.
In the third embodiment, the second blocking material 31 is formed of an elastic material, and the portion in contact with the heat collecting plate 4 is provided with a spring property. Other configurations are the same as those of the second embodiment.
According to the third embodiment, in addition to the effects of the second embodiment, since the second blocking material 31 is provided with a spring property, the contact between the second blocking material 31 and the heat collecting plate 4 is improved. There is.

FIG. 5 is a side sectional view of an essential part showing Embodiment 4 of the present invention, and FIG. 6 is a plan sectional view showing a second blocking material.
In the fourth embodiment, a plurality of weights 42 are fixed to the outer peripheral portion of the second blocking member 41 so as to be in contact with the vertical wall 23 of the housing 2, and other configurations are the same as those of the first embodiment. The same. Therefore, the second blocking material 41 is the same as the second blocking material 15 of the first embodiment and is placed on the heat collecting plate 4.
According to the fourth embodiment, in addition to the effects of the first embodiment, since the weight 42 is attached to the second blocking material 41, the second blocking material 41 is placed on the heat collecting plate 4 and stabilized. There is an effect.

FIG. 7 is a side sectional view of a main part showing Embodiment 5 of the present invention.
In the fifth embodiment, the second blocking member 51 is supported by the spring 52 from the lower side of the heat collecting plate 4 and brought into contact with the back surface of the heat collecting plate 4.
Note that the second blocking member 51 is attached to a support 53 formed of a thermal insulator having the same shape as the second blocking member 51 in detail, and the support 53 is attached by a spring 52 to the heat collecting plate 4. The second blocking member 51 is brought into contact with the back surface of the heat collecting plate 4 so as to be pressed against.
When the second shielding material 51 is formed of a thermal insulator, a metal thin film having a small infrared emissivity is formed on the surfaces of the second shielding material 51 and the support 53 to reduce loss due to radiant heat transfer. Like that. Other configurations are the same as those of the first embodiment.
According to the fifth embodiment, it has the same effect as the first embodiment.

FIG. 8 is a side sectional view of a main part showing Embodiment 6 of the present invention.
In the sixth embodiment, the second blocking member 61 is formed of a thermal insulator in a frame shape, for example, a cylindrical shape, and supports the peripheral portion of the heat collecting plate 4 from the lower side, The gap 13 is closed.
The second blocking material 61 is made of a heat-insulating material having heat resistance, for example, glass or ceramics, and its outer diameter is substantially equal to the inner diameter of the housing 2 as in the above-described embodiment, and the inner diameter is concentrated. The hot plate 4 is made smaller than the outside diameter at normal temperature.

The upper end face of the second blocking member 61 is inclined from the outside to the inside as shown in the figure. This is because the contact between the second blocking member 61 and the heat collecting plate 4 is not a surface contact but a line contact to reduce heat loss.
Even if this inclination is inclined from the inside to the outside, the same effect is exhibited. Even if the upper end face is horizontal, the loss due to conduction heat transfer is slightly increased, but the blocking effect is the same.

Since the outer periphery of the second blocking member 61 is in contact with the inner periphery of the housing 2, the inner periphery of the second blocking member 61 is made smaller than the outer periphery when the heat collecting plate 4 is at a low temperature, The gap 13 between the heat collecting plate 4 and the housing 2 is always closed by the second blocking material 61, and radiation that escapes to the outside through the gap 13 is always blocked by the second blocking material 61.
In addition, a metal foil, which is a metal thin film having a low infrared emissivity, is attached to the surface of the second blocking material 61 so as to reduce loss due to radiant heat transfer. Other configurations are the same as those of the fifth embodiment.
According to the sixth embodiment, in addition to the effects of the fifth embodiment, the second blocking member 61 has an advantage of supporting the heat collecting plate 4 horizontally.

FIG. 9 is a side sectional view of an essential part showing Embodiment 7 of the present invention.
In the seventh embodiment, the second blocking member 71 is formed in a ring shape with a metal plate or a plate-shaped thermal insulator, and the second insulating member 71 is attached to the vertical wall 23 of the casing 2. It is supported by a support 72 made of metal. Further, the support 72 may be formed in a cylindrical shape having a length reaching the bottom of the housing 2 as shown in FIG.
The upper end surface of the second blocking material 71 has the same inclination as in the sixth embodiment, and the second blocking material 71 and the support 72 have the same effect as the second blocking material 61 in the sixth embodiment.
When the second blocking material 71 is formed of a thermal insulator, a metal thin film having a low infrared emissivity is formed on the surfaces of the second blocking material 71 and the support 72 to reduce loss due to radiant heat transfer. Like that. Other configurations are the same as those of the sixth embodiment.
According to the seventh embodiment, there are the same effects as the sixth embodiment.

The radiation loss from the heat collecting plate 4 includes not only the loss from the gaps 12 and 13 but also the loss directly radiated from both the front and back surfaces of the heat collecting plate 4. The loss prevention means is also described in Patent Document 1 and will be described briefly.
The secondary radiation from the surface of the heat collecting plate 4 facing the sunlight is determined by the performance of the selective absorption film attached to the surface and will not be discussed here.

The quality of the method of reducing the loss due to the secondary radiation radiated from the back surface of the heat collecting plate 4 is one of the important factors that determine the performance of the vacuum solar heat collecting device.
Since the heat collecting plate 4 is made of metal, the emissivity from the back surface of the heat collecting plate 4 varies depending on the type of metal, the state of the surface, the wavelength, etc., but the temperature range (30 ° C. to 30 ° C.) At the wavelength of secondary radiation (5 to 15 microns) at 150 ° C., the emissivity is almost the same for many metals. In particular, the emissivity of the surface made by vacuum deposition is small, smaller than the surface made by polishing or sputtering, and is about 0.015 to 0.025 (see the section of spectral reflectance of metal surfaces in the science chronology). ).

  Therefore, in order to reduce the loss due to the infrared radiation of the secondary radiation radiated from the back surface of the warmed heat collecting plate 4, the back surface of the heat collecting plate 4, the bottom portion of the housing 2 facing this, and the window glass 3 are supported. A thin film of metal such as gold, silver, copper, or aluminum is attached to the surface of the pillar 8 or the like, and radiation is suppressed by utilizing the high reflectance (low emissivity) with respect to infrared rays of these thin films. All of these metals have high reflectivity, but copper is suitable because it has good performance and is inexpensive.

The adverse effect of the adsorbed gas such as the housing 2 and the heat collecting plate 4 spreading into the housing 4 is almost eliminated by the baking process in the manufacturing process, but the back surface of the heat collecting plate 4 and the bottom of the housing 2 are still present. Placing a getter material on a part of this will help maintain a long-term vacuum.
The metal for reducing infrared radiation from the back surface of the heat collecting plate 4 and the bottom of the housing 2 and the getter material can be used together.
Therefore, aluminum is selected from many metals having good reflectivity with respect to the infrared rays described above.

The reason for choosing aluminum among many metals is that aluminum is also a getter material that adsorbs gas.
In other words, aluminum is used as the metal for forming the vapor-deposited thin film, the radiation loss is reduced by utilizing the high reflectivity in the far infrared region of aluminum, and the window glass is obtained by utilizing the getter function of aluminum that adsorbs gas. By adsorbing the gas that exudes from the metal of 3 and the housing 2, the high vacuum inside the housing is maintained for many years.

In order to maintain a high vacuum for a long period of time, the vacuum flat plate type solar heat collecting apparatus of the present invention is in a high vacuum and high temperature for driving out adsorbed gases such as the housing 2 and the window glass 3 during the manufacturing process. A long baking process is built in.
Since the degree of vacuum in the process is maintained at about 0.001 Pascal, aluminum is vacuum-deposited on the back surface of the heat collecting plate 4 and the bottom of the housing 2 facing it during the process.

When baking is performed in the manufacturing process of the solar heat collecting apparatus, the pillar 8 is also erected in the housing 2, and the heat collecting plate 4 also includes first and second blocking members 14 and 15 for closing the gaps 12 and 13. Since the vacuum deposition device is placed between the heat collecting plate 4 and the bottom plate of the housing 2 and vacuum deposition is performed, aluminum is vacuum deposited on all of these members. Very useful for improving efficiency.
Further, since the gaps 12 and 13 are also closed, aluminum is not deposited on the window glass 3.

  In the above-described embodiment, a circular vacuum flat plate solar heat collecting device is illustrated as an example, and each component is described. However, when the device is square, the shape is square accordingly. Is natural.

It is a figure which shows Example 1 of this invention. It is a figure explaining the magnitude | size of a 1st shielding material. It is a sectional side view of the principal part which shows Example 2 of this invention. It is a sectional side view of the principal part showing Example 3 of the present invention. It is a sectional side view of the principal part which shows Example 4 of this invention. It is a sectional side view which shows the 2nd shielding material of Example 4. It is a sectional side view of the principal part which shows Example 5 of this invention. It is a sectional side view of the principal part showing Example 6 of the present invention. It is a sectional side view of the principal part showing Example 7 of the present invention.

Explanation of symbols

2 Housing 3 Window glass 4 Heat collecting plate 8 Column 9, 10 Tube 11 Hole 12, 13 Gap 14 First blocking material 15, 21, 31, 41, 51, 61, 71 Second blocking material 22 Vertical portion 23 Vertical wall 42 Weight 52 Support 72 Support

Claims (11)

A window glass, a casing, a plurality of pillars for supporting atmospheric pressure between the window glass and the bottom of the casing, and a hole having a size through which the pillars penetrate and do not contact are provided in the housing. In a vacuum flat plate solar heat collecting apparatus provided with a heat collecting plate,
Even if the column is inserted and has a hole slightly larger than the outer periphery of the column, even if the heat collecting plate is thermally expanded and the hole of the heat collecting plate is moved, a gap between the heat collecting plate and the column A first shielding member formed of a metal plate or a plate-like thermal insulator having a size capable of closing the wall is passed through the column and placed on the heat collecting plate, and the heat collecting plate and the column, Block the gap between
A second barrier material made of a metal plate or a plate-shaped thermal insulator having an outer periphery of a size in contact with the inner periphery of the housing and having an inner peripheral hole smaller than the outer periphery of the heat collecting plate. A vacuum flat plate solar heat collecting apparatus, which is placed on a hot plate and closes a gap between the heat collecting plate and the casing.   2. The vacuum flat plate solar collector according to claim 1, wherein a selective absorption film is formed on the upper surfaces of the first and second blocking materials.   The vacuum flat plate solar collector according to claim 1 or 2, wherein a vertical portion is formed in a peripheral portion of the second blocking material, and a plurality of portions of the vertical portion are fixed to a vertical wall of the casing. .   4. The vacuum flat plate solar heat collecting apparatus according to claim 3, wherein the second blocking material is made of an elastic material, and a portion in contact with the heat collecting plate has a spring property.   The vacuum plate type solar heat collecting apparatus according to claim 1 or 2, wherein a plurality of weights are fixed to an outer peripheral portion of the second blocking member so as to contact a vertical wall of the casing. A window glass, a casing, a plurality of pillars for supporting atmospheric pressure between the window glass and the bottom of the casing, and a hole having a size through which the pillars penetrate and do not contact are provided in the housing. In a vacuum flat plate solar heat collecting apparatus provided with a heat collecting plate,
Even if the column is inserted and has a hole slightly larger than the outer periphery of the column, even if the heat collecting plate is thermally expanded and the hole of the heat collecting plate is moved, a gap between the heat collecting plate and the column A first shielding member formed of a metal plate or a plate-like thermal insulator having a size capable of closing the wall is passed through the column and placed on the heat collecting plate, and the heat collecting plate and the column, Block the gap between
A second barrier member made of a metal plate or a plate-shaped thermal insulator having an outer periphery of a size in contact with the inner periphery of the housing and having an inner peripheral hole smaller than the outer periphery of the heat collecting plate is viewed from below. A vacuum flat plate solar heat collecting apparatus characterized in that a gap between the heat collecting plate and the casing is closed by supporting with a spring. A window glass, a housing, a plurality of pillars for supporting atmospheric pressure between the window glass and the bottom of the housing, and a hole having a size through which the pillars penetrate and do not contact are provided in the housing. In a vacuum flat plate solar heat collecting apparatus provided with a heat collecting plate,
Even if the column is inserted and has a hole slightly larger than the outer periphery of the column, even if the heat collecting plate is thermally expanded and the hole of the heat collecting plate is moved, a gap between the heat collecting plate and the column A first shielding member formed of a metal plate or a plate-like thermal insulator having a size capable of closing the wall is passed through the column and placed on the heat collecting plate, and the heat collecting plate and the column, Block the gap between
A heat insulating material having an outer periphery that is in contact with the inner periphery of the housing and having an inner peripheral hole smaller than the outer periphery of the heat collecting plate is formed in a frame shape, and is installed on the inner periphery of the housing. A vacuum flat plate solar heat collecting apparatus, wherein a gap between the heat collecting plate and the housing is closed by supporting a peripheral portion of the heat collecting plate with two shielding materials. A window glass, a casing, a plurality of pillars for supporting atmospheric pressure between the window glass and the bottom of the casing, and a hole having a size through which the pillars penetrate and do not contact are provided in the housing. In a vacuum flat plate solar heat collecting apparatus provided with a heat collecting plate,
Even if the column is inserted and has a hole slightly larger than the outer periphery of the column, even if the heat collecting plate is thermally expanded and the hole of the heat collecting plate is moved, a gap between the heat collecting plate and the column A first shielding member formed of a metal plate or a plate-like thermal insulator having a size capable of closing the wall is passed through the column and placed on the heat collecting plate, and the heat collecting plate and the column, Block the gap between
A second barrier member made of a metal plate or a plate-shaped thermal insulator having an outer periphery that is in contact with the inner periphery of the housing and having an inner peripheral hole smaller than the outer periphery of the heat collecting plate is provided in the housing. Supporting from below with a support attached to the body, and supporting a peripheral portion of the heat collecting plate with the second blocking material, thereby closing a gap between the heat collecting plate and the housing. Vacuum flat plate solar collector.   The vacuum flat plate solar heat collecting apparatus according to any one of claims 6 to 8, wherein a selective absorption film is formed on an upper surface of the first blocking material.   The vacuum plate type solar heat collecting apparatus according to any one of claims 1 to 9, wherein a metal thin film having a small infrared emissivity is formed on a surface of the thermal insulator.   The vacuum plate type solar heat collecting apparatus according to any one of claims 1 to 10, wherein an aluminum thin film is vapor-deposited on a back surface of the heat collecting plate and a bottom portion of the housing facing the heat collecting plate.

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