JPS59164852A - Overheat inhibitor for solar heat collector - Google Patents

Abstract

PURPOSE:To limit the maximum temperature of the titled device when the device is out of water at the time when the sun is in the south so that deterioration of a heat collector may be prevented by installing a heat storing material in a heat collecting pipe or header. CONSTITUTION:In a solar heat collector of a plate type or of a vacuum tube type comprising a glass sheet 1, heat insulating material 6, heat collecting pipe 2 and header 8 (condensation section), heating maxium temperature void of water at the time when the sun is in the south by installing a heat storing member 11 in the heat collecting pipe 2 or header 8. For such heat storing member 11, organic material such as high density polyethylene is used for the flat plate type, and inorganic material such as molten salt of NaCl for the vacuum tube type. As the heating temperature of the heat collector void of water can be controlled by installing the heat storing material, the deterioration of the heat collector can be prevented.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a mechanism for preventing overheating of the internal structure of a solar heat collector when two houses are fired when there is no cooling water for the solar heat collector, and in particular, This relates to a highly reliable air space j4 measure that increases the heat capacity near the heat tube.

[Prior art]

Conventional solar thermal collectors often do not take measures against dry heating on the collector itself, and the system side has to constantly supply cooling water, but the drawback is that the system may run dry due to pump failure, etc. there were. In the conventional example of a flat plate type heat collector with a natural circulation heat pipe as shown in FIG. A working fluid 3 (freon is used because water easily freezes) was circulated by gravity in a thermosiphon type, and the cooling water 5 inside the header cover 4 was heated by the heat pipe condensing section 8. During dry firing when the cooling water 5 runs out, the temperature of the heat pipe reaches 130C or more, which causes the heat medium Freon to decompose, resulting in a decrease in heat pipe performance. The reason why the dry firing temperature is extremely high is that the heat pipe is insulating material 6 (made of glass wool, urethane) inside the outer box 7.
This is because there are reeds inside, so there is less heat dissipation. When the dry firing temperature becomes high, the urethane and rubber parts deteriorate, and the performance of the light selective absorption surface on the surface of the heat collecting plate 9 may also deteriorate due to the vapor.

Straight-pipe heat collectors, in which cooling water flows directly into the heat collection tubes of flat-plate heat collectors, use antifreeze (ethylene glycol, etc.) to prevent freezing, but when the heat is empty, the temperature rises and the antifreeze The problem was that it decomposed.

Even when using a heat pipe heat collector tube for a vacuum tube type heat collector,
If water is used as a heat medium (which has the best performance), there is a drawback that the heat pipe will burst due to the vapor pressure of the water when the temperature is 2000 or more.

There are materials (such as Frutic) that are resistant to dry firing and freezing as a heat medium for heat pipes, but the heat collection efficiency is about half that of using water. There is a conventional method of flowing silicone oil etc. through forced circulation type heat collecting pipes, but this method has the drawbacks of high pump cost and expensive materials.

[Purpose of the invention]

The purpose of the present invention is to keep the dry temperature of the solar heat collector constant? /,
? It is overcome by providing simple overheat prevention 41ia 't'f etc. inside the heat collection on the 7th leg below the +j back. The maximum dry-fired temperature when there is no cooling water in the collector is -[14? Generally, the temperature exceeds the allowable temperature of the heat collector material.

The aim is to suppress this dry firing (v1 degree peak) with a reliable 11.6-degree pure method that has no dynamic parts.

[Summary of the invention]

In order to achieve the above objective, we focused on a method of increasing heat capacity by adding a heat storage body to the heat collecting pipe. Conventional heat collecting tubes have a small heat capacity, so their time constant (63mm response time)
It lasts for several minutes, and the sky-fired temperature reaches its highest value when the sun is at its midpoint, and decreases as the sun's altitude decreases to 7. It was noted that if latent heat (melting, etc.) is used as a heat storage material, the maximum temperature of the dry firing can be lowered, and when the heat is radiated (solidified) in the afternoon, the time constant is on the order of hours.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. Sunlight 117F passes through the glass plate 1 and is collected into the heat collecting tube 2 (heat pipe) through the heat collecting plate 9.

Freon, which has a low freezing temperature, is used as the heat medium 3 in the heat pipe, and solar heat is transferred to the cooling water 5 inside the bender cover 4 in the heat pipe condensing section 8.

The cooling water circulates naturally, collecting heat during sunshine on a sunny day and using the hot water in the late afternoon. This type of heat collector is a natural circulation heat pipe type flat plate type.

There is a heat insulating material 6 between the outer box 7 and the heat collecting pipe 2 to reduce heat radiation to the lower part, and the temperature of the heat pipe reaches 130 tl' or more during dry firing when there is no cooling water 5. . In this case, the freon of the heat pipe heat medium is thermally decomposed, resulting in deterioration of its performance. By installing a heat storage tank IO below the heat collecting pipe 2 and heat collecting plate 9 and injecting a heat storage material, the dry firing temperature can be lowered from its maximum value. High-density polyethylene is suitable as the heat storage interest in this case. The reason is that high-density polyethylene has a relatively low latent heat of fusion (about 25.0 J/g) and a high density (about 22/crI).
This is because it is cheap (approximately 1 to 7 yen). Heat storage No. 4,
After being sealed in a heat storage tank, it is brought into contact with an annual heating element. To improve heat transfer, polyethylene, which does not change shape even when melted, can be directly sealed inside the heat pipe.

FIG. 3 shows the effect of this embodiment. Conventionally, when the sun is at its mid-sunset, the air-fired Ai? Although the high temperature IW reached 170tZ',
According to the present invention, the maximum temperature can be lowered to 130C. In the present invention, when the empty firing temperature reaches 120C in the morning, the polyethylene melts and remains at 20C for about 1 hour. Solar heat incidence for one heat pipe: one piece (approximately i
oow, so 1.8 kf of polyethylene is required. When the heat storage side melts, the dry firing temperature rises a little and reaches 130r, but in the afternoon the sun's altitude is low and υ
, the 120C polyethylene solidifies again. In this way, according to this embodiment, the dry firing temperature can be lowered to 1301r or less, thereby preventing the thermal decomposition of Freon in the heat pipe.
It has the effect of allowing F.

No. 41. <l tri, % Overheat prevention of straight air tube type heat collector with heat pipe t1 (This is a conventional example of 1. The great sunlight passes through the vacuum glass t1 and is collected into the heat tube 2. The heat g^ body 3 in the heat pipe is transferred to the heat pipe condensing section 8.
Go back and forth between. j'IV'IA body material is 10
Water with good heat transport properties at around 0C is used, but when dry-fired (
250tZ"), there was a drawback that the heat pipe (copper) would burst due to high pressure. Conventional measures against dry firing were ゛-\
Heat pipe 1 with gas in the tube (heat pipe condensing part)
2 was provided, and a method was used in which the heat was radiated using the heat radiation fins 13 only when the fire was dry. However, gas-filled heat pipe t'', -
- There was a problem with watertightness because the rudder cover 4 was transparent, and the heat dissipation fins were deformed in strong winds.

1 in Figure 5, heat storage in part of the header in Figure 4 4'1tI11
Embodiment A of the present invention in which vinegar material 11 is sealed by using
-Smart. This overheating prevention mechanism is simple compared to gas heat pipes. Taking into consideration that the heat storage temperature is also high at the empty firing temperature of the vacuum tube type heat collector at %300C, N, C1-B, C4 eutectic salt (1: I''lA 220'C ) '14) Use.

- Since the ladder is usually made of copper, it is necessary to pay attention to its coexistence with heat storage materials.

FIG. 6 shows an embodiment of the present invention in which a heat storage material is encapsulated in the capsule 10 and closely colored around the header. Cub-1
= The paulownia material is made of stainless steel, and it is used throughout the city as a heat storage material.
It is about 2xp. FIG. 7 shows the effect of this embodiment -J-
The time it takes for the eutectic salt to melt is about 20 minutes, and the temperature rises a little even in the morning when the sun is in the south. However, when compared with the highest value of the dry firing temperature of the conventional example, this example has a temperature of 35. tl
There is a difference of 1", which is less than 2'45U. At this level of dry firing temperature, the water vapor pressure inside the heat pipe is 3.
It was found that the heat pipe had a pressure of 6 atmospheres, did not burst, and had a lifespan of over 10 years.

Figure 8 shows a true tube type flat plate collection 1. This is an embodiment of the present invention for a container. A header is provided upstream of this heat collector, and the cooling water 5 is forcibly circulated through the straight pipes 2 arranged in a similar manner. In order to install the slope 1 with the upstream ladder on the upper side,
The temperature of the upper straight pipe becomes 1rrl even when the fire is empty.

Therefore, the heat storage material 11 is installed in the upper straight pipe of the Cub-Hill 10, in which one person is placed, as a countermeasure against dry firing.

If measures are not taken to prevent dry firing, if the pump stops while the straight pipe is filled with cooling water, the antifreeze in the cooling water will decompose due to high humidity. When high-density polyethylene is used as a heat storage material,
Since the temperature of the cooling water can be suppressed to 120C or less, the lifespan of the antifreeze will be extended.

FIG. 9 shows an embodiment of the present invention directed to a U-shaped vacuum tube type heat collector. Cooling water 5 is supplied to U in the vacuum glass tube 1.
It passes through the inside of the straight pipe 2. There are 9 heat collecting plates installed on the top of the straight pipe, and when the temperature is dry, the temperature reaches nearly 300C, which may deteriorate the ΔT selective absorption membrane.Furthermore, if the cooling water pump is stopped and the heat is heated dry, the antifreeze (enalenocricol, etc.) decomposes.

Therefore, if the capsule 10 containing the stored 6 months 11 is installed in the header 7 (IS), the same effect as described above can be obtained.

[Ga--light effect]

According to the present invention i, 1. Since the dry heating temperature of the heat collector can be suppressed, there is an effect of preventing deterioration of the heat collector. In the case of flat-plate heat collectors, if measures are taken to prevent dry heating, the maximum temperature of the heat collecting pipes can sometimes approach 2001: [1°C].

In this case, in the case of a natural circulation type heat pipe of flat plate type, the heat pipe heat medium (Freon, etc.) decomposes and the performance deteriorates. According to the present invention, when polyethylene is used as the storage material, the maximum temperature I during dry firing can be suppressed to 130C. Forced circulation 1:1 If you put antifreeze in the cooling water and dry it in a flat plate type, the antifreeze will overflow, but this invention can prevent this. [←, I can.

Vacuum 21゛January In the case of a heat collector, the empty firing temperature is 300
11. , jl, the Y heat pipe container would burst if there were 4 people with a heat pipe, but the present invention can reduce the temperature to below 240C. Compared to the conventional dry firing countermeasure using a gas-filled heat pipe, the overheating prevention method of the present invention is simple and has good effects at about 50% of the cost.

The heat storage material of the present invention also has the effect of being able to check the remaining heat when the cooling water 4 is used again in the afternoon for TOKYO HOT.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a natural circulation type heat collector (sub;
, Comparison diagram of dry firing temperature, Fig. 4 is an explanatory diagram of conventional dry heating countermeasures for vacuum tube type heat collector, Fig. is a vertical sectional view showing another example of this header, Fig. 7 is an explanatory diagram of the effect of the embodiment of Fig. 6, and Fig. 8 is an explanatory diagram of an application example to a forced circulation flat plate type. The figure is an explanatory diagram of an embodiment of a U-shaped vacuum tube type. 1... Glass plate (tube), 2... Heat collecting tube (heat pipe), 3... Heat medium, 4... Header cover,
・Cooling water, 6...Insulation material, 7...Outer box, 8...Condensing part (hengu), 9
o ・・・１′桿Fり舊い会、1 １． ”' Dari ←〆〆5 Ishi 1, l 2...Gas-filled heat pipe, 13...Radiating fin. You/Me C/x-x' Sho 7 Figure x-X' Kohai 11 ('h] Chapter Figure 5 Funeral G Diagram q Figure 15 Support 11 (h)

Claims (1)

[Claims] 1. In flat plate type and vacuum tube type solar heat collectors consisting of glass, heat insulating material, heat collecting pipes, and headers, a heat storage material is installed in the heat collecting pipes or ladders, and dry firing is possible during the solar zenith. An overheating preventer for solar heat collectors, which is characterized by lowering the maximum temperature. 2. In the first claim, the material for the heat storage material is an organic material such as high-density polyethylene, vacuum 9°F for flat plate type, etc.
An overheating preventer for a solar heat collector, characterized in that an inorganic substance such as N or Ct eutectic salt is used for the shape.