JPS604036Y2 - solar heat collector - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a solar heat collector that uses water as the working fluid to prevent the working fluid from freezing from above and to prevent damage due to bursting of heat pipes.

In general, a heat pipe type solar heat collector coaxially inserts the evaporating part of the heat pipe with heat collection fins fixed into a permeable outer tube installed at an angle, and the heat insulating part of the heat pipe and condensation It has a structure in which the heat exchanger part protrudes above the permeable outer tube and the heat exchange part is directly connected to the condensing part.The permeable outer tube is usually sealed and the inside of the outer tube is evacuated to a vacuum in order to insulate it from the outside. The heat collecting fins are coated with a selective absorption film.

By the way, if water is used as the working fluid of the heat pipe,
When the outside temperature drops below the freezing point, such as in winter, and the water is left unloaded, water has the highest specific gravity at 4℃, so water with a low specific gravity that has been cooled to near O'C will be compared to water with a high specific gravity. It rises to the top, solidifies into ice starting from the top, expands in volume, and freezes in the heat pipe, applying pressure to the water at the bottom.

As a result, the lowest part of the heat pipe bursts and is damaged.

Conventionally, the freezing point of the hydraulic fluid is lowered by mixing a solvent or the like with the water used for the hydraulic fluid, or by using a fluid with a low freezing point other than water as the hydraulic fluid to prevent the hydraulic fluid from freezing. This prevents damage due to heat pipe bursting.

However, if the usage range of solar heat collectors is from 0℃ to 100℃, a working fluid that uses only water is the best in terms of price.
Both of the above-mentioned hydraulic fluids have the disadvantage that they are more expensive than hydraulic fluids made only of water.

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

In the drawings, reference numeral 1 denotes a transparent outer tube made of glass or the like, which is hermetically sealed and evacuated to a vacuum inside, and is installed at an angle.

2 is a heat pipe using water as a working fluid; 3 is an evaporating section of the heat pipe 2 inserted into the permeable outer tube 1; 4 is a condensing section of the heat pipe 2 protruding upward from the permeable outer tube 1;
is a heat exchange part directly connected to the condensing part 4, 6 is a heat collecting fin fixed to the evaporating part 3, 7 is a selective permeation film applied to the heat collecting fin 6, and 8 is black paint applied to the lower end of the heat collecting fin 6. This is a non-selective absorption membrane made by the heat pipe 2, which increases the heat dissipation from the lower part of the working fluid of the heat pipe 2 in the no-load state.

Next, the operation of the embodiment will be explained.

If the outside temperature drops below the freezing point during winter and the heat pipe is left unloaded, the water used as the working fluid for the heat pipe 2 will
Since the heat dissipation in the 8 parts of the non-selective absorption film applied to the lower end of the heat collecting fin 6 is larger than that in the 7 parts of the selective absorption film, the lower part approaches 0°C earlier than the upper part, and as the specific gravity becomes smaller, it tends to rise. Convection occurs and the temperature approaches 0°C overall, but the temperature difference between the upper and lower parts decreases and the convection speed slows down. The heat pipe 2 solidifies into ice and freezes in the heat pipe 2 starting from the lower end, thereby preventing the heat pipe 2 from bursting.

As described above, according to the solar heat collector of this invention, the evaporation part of a heat pipe with heat collecting fins fixed to it is inserted into the permeable outer tube, a selective absorption film is applied to the heat collecting fins, and the heat pipe is coated with a selective absorption film. In solar heat collectors that use water as the working fluid, by applying a non-selective absorption film to the lower end of the heat collecting fin, it is possible to prevent the working fluid from freezing from the top and also prevent damage due to heat pipe bursting. Moreover, it is possible to use only water as a working fluid and is inexpensive.

[Brief explanation of drawings]

The drawing is a perspective view of one embodiment of the solar heat collector of this invention. 1... Permeable outer tube, 2... Heat pipe, 3... Evaporation section, 6... Heat collection fin, 7... Selective absorption membrane, 8...Non-selective absorption membrane.

Claims (1)

[Scope of utility model registration request] In a solar heat collector in which an evaporation part of a heat pipe with heat collecting fins fixed to a permeable outer tube is inserted, a selective absorption film is applied to the heat collecting fin, and water is used as a working fluid of the heat pipe, A solar heat collector in which a non-selective absorption film is applied to the lower end of the heat collecting fin.