JPS59119143A - Heat medium of solar heat collector - Google Patents

Abstract

PURPOSE:To inhibit a heat medium pipe from being corroded, to prevent the heat medium pipe from being oxidized even when a solar heat collector is operated at high temperatures withut load, to prevent wet corrosion of the heat medium pipe and to disperse scale, by using water as a heat medium to which a boron compound and benzotriazole or its derivative. CONSTITUTION:The water to which a boron compound such as sodium borate and benzotriazole or a benzotriazole derivative is used as a liquid to be circulated through plates for collecting solar heat. Not only the heat medium can be readily prepared, but also if it is applied in the most widely used solar heat collector using steel pipes wherein the heat medium heated in a heat collector is taken out therefrom to be used, the heat collector and the piping can be inhibited from being corroded and the heat medium pipe can be prevented from being oxidized.

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a liquid heat medium used in a solar heat collector,
In particular, it relates to heat grinding that suppresses the corrosive effect of water and the adhesion of scale.

(b) Conventional art There are structures of solar heat collectors as shown in FIGS. 1 and 2. In each figure, (1) is a heat collecting plate that receives solar radiation heat, and (2) is a heat medium pipe for transmitting the heat collected by this heat collecting plate (11) to a heat medium. The plate (1) and the heat medium pipe (2) are often installed in the atmosphere, but when collecting heat at a particularly high temperature or with high efficiency, the heat collecting plate (11) and the heat medium pipe (2) are (2) is stored in a Minoku container (3) such as a vacuum glass tube.

In addition, some solar heat collectors use a special liquid as the heat medium, and many use water as the heat medium. However, when water is used for ms, heat transfer pipe (
2) Depending on the quality of the water passing through, there is a risk that scale may adhere to the inside of the pipe or corrode the pipe wall. In particular, if the heat collector plate is exposed to solar radiation with the water circulation stopped, the water in the heat medium pipe (2) will boil and reduce, resulting in an empty heating state. ), scale adhesion and corrosion are likely to occur inside.

For this reason, water treatment agents have traditionally been added to prevent corrosion and scale, but if the water treatment agent is not selected appropriately, the agent may remain in the pipes.
Its components may induce corrosion, and silicic acid content (N a2
When S i', O, ), etc. are present, this component accumulates in the tube as scale, which has the disadvantage of reducing the heat exchange efficiency as a heat collector.

(c) Purpose The present invention was developed in view of the above points, and is intended to be used as a heat medium for solar heat collectors, to suppress corrosion of the heat medium pipes of the device, and to retain heat even when heated dry at high temperatures. The purpose is to provide an aqueous heat medium that can prevent oxidation of medium pipes, prevent cross-contamination, and disperse scale.

B) Structure and Examples In the present invention, water to which a boron compound and benzo-IJ azole or a derivative thereof is added is used as a heat medium circulating in the heat collecting plate of a solar heat collector.

The amount of addition is as follows: boron compound (up to 2%/small quantity, benzo), IJ azole or its derivative (1%/
Each is used by dissolving it in water in minute amounts of up to q.

Boron compounds dissolve in water to make the water alkaline and at the same time act as corrosion protection for the steel connected to the solar collector. In addition, even when dry heating occurs in the heat transfer pipe (2), the boron compound does not evaporate and remains inside the heat transfer pipe (2) to prevent corrosion of copper and copper alloys and to prevent scale adhesion. It is.

In addition, benzotriazole and its derivatives are heat resistant and have a high boiling point (as well as providing corrosion protection for copper and copper alloys,
These materials are adsorbed in molecular form on the inner surface of pipes and act as anti-scaling agents.

FIG. 3 is an example of a test device for confirming the performance of the heat medium according to the present invention.

In the figure, (4) (4) is a conduit in which a heating medium is sealed;
(5 + (5) is a liquid tank that adjusts the physical conditions on the open end (6) (6') side of the conduit, (7) (7) is an oil vent with an opening/closing cock (8 on 8) and conduit (4) (
Most of 4) is housed in a heating furnace 01) equipped with an electric heater 00) equipped with a calorific value controller (9).

Table 1 shows that in such a device the conduit (4) (4'
) is made of copper or copper alloy, and the liquid tank (
A steel piece 02) was placed in the solution of 61 (6), 300 ng/l of benzotriazole was added to ice water as a heating medium, and 8001 ng/l of sodium borate (NaJLOJ) was added as an example of a boron compound.
This figure shows the results of tests under various heating temperature conditions using water (test heating medium) dissolved at a ratio of 1.1 and ordinary tap water for comparison.

The results in the table can be seen as the results of a type of dry firing test. ○ in the table indicates that the surface of the conduit remains in good condition even after the test period, and △ indicates that the surface is oxidized to some extent but is in good condition to the extent that no peelable film or corrosion occurs. The copper ion column on the far right shows the analysis results of the heating medium after completing these series of dry firing tests.

As is clear from this table, the heat medium of the present invention is clearly better than tap water, and such results are
Even when compared with other commercially available heating media, it was confirmed to be a more preferable value.

(e) Effect The present invention uses water as a solvent (in addition to this, a boron compound is added to prevent corrosion of copper, and benzotriazole or its derivatives, which are relatively stable even at high temperatures, are added to prevent corrosion of steel and copper. Since it is added as a heating medium for solar collectors, it is not only possible to obtain the heating medium extremely easily (but also when copper or copper alloy material is used for the collector, and when heated by the solar collector). In the most popular type of solar heat collector, which uses steel pipes to lead the heat medium outside the device, it is possible to suppress corrosion of the heat collector and piping, and prevent oxidation of the heat medium pipes. be.

In particular, boric acid compounds do not evaporate even when the heat collector is fired dry, and remain in the pipes of the heat collection section to protect metal from corrosion, while also having the function of dispersing scale components. It can also reduce the risk of lowering the heat exchange efficiency of the heater, and is particularly effective in solar heat collectors that collect high-temperature heat.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an example of a solar heat collector, FIG. 2 is a cross-sectional view showing another example, and FIG. 3 is a schematic diagram showing an example of a heating medium test device according to the present invention. . (1)... Heat collection plate, (2)... Conduit agent Patent attorney f Seal review Inu-11 Figure 1 Figure 2

Claims (1)

[Claims] (1) Boric acid) A heat medium for a solar heat collector, characterized in that water to which a boron compound such as IJum and benzotriazole or a benzotriazole derivative is added is used as a liquid to be circulated in a heat collecting plate for solar radiant heat. .