JPS5930864Y2 - solar heat collector - Google Patents

Description

[Detailed description of the invention] This invention is designed to prevent damage to the heat pipe due to freezing by freezing the working fluid from the lower part of the heat pipe when the working fluid of the heat pipe freezes. This is what I did.

A conventional solar heat collector using a heat pipe is constructed as shown in FIGS. 1 and 2.

That is, in those drawings, 1 is a cylindrical translucent outer tube made of glass or the like with one end sealed, 2 is a heat collecting plate installed inside the outer tube 1, and 3 is inserted coaxially into the outer tube 1. It is a sheet pipe for heat collection, and the evaporation part 4 is joined to the heat collection plate 2 in a heat transfer manner.

Reference numeral 5 denotes a stem that closes the opening of the outer tube 1, and the condensing section 6 of the heat pipe 3 is led out from the central portion in an airtight manner.

Reference numeral 7 denotes a working fluid such as water, which is injected in a required amount into the almost evacuated interior of the heat pipe 3, and the interior of the outer tube 1 is evacuated.

Then, the working fluid 7 of the heat pipe 3 is evaporated by the solar heat obtained by the heat collecting plate 2, and the heat is transported to the condensing section 6, where it gives heat to the circulating heat medium and condenses into a liquid.
The condensed liquid returns to the lower part of the heat pipe 3 along the inner wall surface of the heat pipe 3 due to gravity, and heat is collected by repeating the above action.

By the way, when a heat pipe that uses water as the working fluid 7, which is inexpensive, easy to handle, and has good performance, is not in operation, the working fluid 7 accumulates in a column shape, and the installation location of the heat collector is affected. The environment is as low as at night in winter,
When the temperature drops below 0°C, the hydraulic fluid 7 freezes.

At this time, the entire columnar hydraulic fluid 7 begins to freeze, and the hydraulic fluid 7
The heat pipe 3 is damaged due to volumetric expansion due to freezing.

This idea was made with the above points in mind,
Next, this invention will be explained in detail with reference to FIGS. 3 and 4 showing one embodiment thereof.

In these drawings, the same symbols as in FIGS. 1 and 2 above indicate the same things, and the difference is that a thin, pointed heat dissipation pin 8 is provided at the bottom of the heat pipe 3. , the upper side of this pin 8 is immersed in the working fluid 7 of the heat pipe 3, and is made of a material with good thermal conductivity such as copper,
Additionally, in order to increase the radiation rate, a coating such as black paint is applied, resulting in a high radiation encapsulation with a small surface area.

On the other hand, in a vacuum glass tube type solar heat collector where the outer tube 1 is made of glass, the inside of the outer tube 1 is vacuum insulated, so most of the heat radiation comes from radiant heat, and in the case of freezing etc. The working fluid 7 in the heat pipe 3 is cooled by the heat generated by the envelope between the heat collecting plate 2 and the glass outer tube 1.

Therefore, the heat quantity q of the envelope between the heat collecting plate 2 and the outer tube 1 is
p is approximately given by the following equation using the equation for an infinite parallel plate.

Here, le is the Stefan Boltzmann constant, Tp is the temperature of the heat collecting plate, Tg is the temperature of the glass outer tube, and εp is the radiation rate of the heat collecting plate.Since a selective absorption film is generally applied to the heat collecting plate, εp is The value is close to 0.1.

εp is the emissivity of the glass.

Next, the amount of heat qe in the envelope between the heat dissipation pin 8 attached to the bottom of the heat pipe 3 and the glass outer tube 1 is calculated by the following equation.

□'j e= 0XJ (T64 Tg4) c
'2 Here, Te is the heat radiation pin temperature, and εe is the radiation rate of the heat radiation pin, which is approximately 1.

As is clear from the above two equations, qe>qp, the heat radiation pin 8 radiates more heat than the heat collecting plate 2, and Te<Tp.

Therefore, the working fluid 7 begins to freeze from the bottom of the heat pipe 3 that is in contact with the heat dissipation pin 8 and proceeds to the top in order, and the volumetric expansion due to freezing of the working fluid 7 causes the space above the working fluid 7 to freeze. This prevents damage to the heat pipe 3.

On the other hand, during heat collection, the heat radiation amount per unit area is larger for the heat radiation pin 8 than for the heat collection plate 2, but the surface area of the heat radiation pin 8 is negligible compared to the surface area of the heat collection plate 2. Therefore, the heat loss from the heat radiation pin 8 is extremely small, and the heat collection efficiency does not decrease at all.

As described above, according to the solar heat collector of this invention, by providing a high sealing body with a small surface area at the bottom of the heat pipe, when the working fluid of the heat pipe freezes, the working fluid freezes from the bottom. , damage to the heat pipe can be prevented.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a conventional solar heat collector, Fig. 2 is a partially cutaway front view of Fig. 1, Fig. 3 is a perspective view of one embodiment of the solar heat collector of this invention, and Fig. 4 is a perspective view of a conventional solar heat collector. The figure is a cutaway front view of the main part of FIG. 3. 1... Outer tube, 2... Heat collecting plate, 3...
...heat pipe, 4...evaporation section, 7...
...Hydraulic fluid, 8... Heat dissipation pin.

Claims (1)

[Scope of utility model registration request] A solar heat collector in which an evaporation part of a heat pipe is inserted into a translucent outer tube and the inside of the outer tube is evacuated, and a high encapsulation body with a small surface area is provided at the bottom of the heat pipe.