JPH04190049A - Heat collecting member - Google Patents

Abstract

PURPOSE:To provide a heat collecting member having a high heat collecting effect by a method wherein the heat collecting member is made of either aluminum or aluminum alloy provided with a surface having a lightness in Munsell color system and a specified reflectance. CONSTITUTION:A surface of a plate member of either aluminum or aluminum alloy machined into a predetermined shape constituting a heat collecting member is processed to form a rough surface. It is preferable that a degree of this rough surface formation is of about Rmax 1000 to 100mum in order to provide a surface reflectance of 30% or less. In case of performing a sand blasting operation, for example, conditions such as a grain size of sand, blasting pressure and a processing time or the like are properly selected and realized. Then, the plate member having its surface rough processed is colored to have a lightness in the gray scale of Nunsell color system of 5.0 or less. This surface coloring process is carried out within hot water with its amount of inclusion of negative ions such as carbonic acid ion, silicon acid ion or the like being about 5 to 200ppm.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heat collecting member, and more particularly to a heat collecting member effective as a heat collecting plate for a solar system that utilizes solar heat.

(Prior Art) A solar system that uses solar heat as a heat source incorporates a heat collecting member such as a heat collecting plate for receiving sunlight and absorbing the amount of heat thereof.

Since this heat collecting member must function to transfer the amount of heat absorbed on its surface to a heat medium such as water flowing inside, it is preferably made of a material having high thermal conductivity. At the same time, in order to efficiently absorb solar heat, it is preferable that the surface be colored blackish gray and have a low reflectance.

For this reason, conventional heat collecting members are generally made of copper, which has the second highest thermal conductivity after silver, partly because it is inexpensive, and have a rough surface and a black color. Colored ones are used.

(Problem to be Solved by the Invention) By the way, solar systems are beginning to become popular in general households as an auxiliary device for producing hot water. In that case, the heat collecting member of the solar system is generally installed on the roof of the house.

In order to increase the amount of hot water produced, it is necessary to increase the heat collecting area of the heat collecting member.

However, as the heat collection area increases, the overall weight of the heat collection member becomes heavier, which increases the load on the house.

Therefore, as a material for the heat collecting member of a solar system, it is preferable that the material has a high thermal conductivity and a low specific gravity. Furthermore, in consideration of its widespread use in general households, it is preferable that the material be manufactured at low cost.

An example of a material that satisfies these conditions is an aluminum member such as aluminum or an aluminum alloy. Aluminum or aluminum alloy
Compared to copper, its thermal conductivity is about 1/2 lower, but its specific gravity is about 1/3, which is lighter, so in terms of its physical properties it is 1. It is a material that can be used as a heat collecting member.

However, the surface of aluminum parts usually shines silvery white and has a very high reflectance to sunlight, so most of the sunlight irradiated here is reflected and absorbed by the aluminum part. The problem is that solar heat is small.

For this reason, to date, no heat collecting member for solar systems made of aluminum members is known.

The present invention solves the above-mentioned problems with aluminum members when used as heat collecting members, and provides a novel aluminum member that exhibits a heat collecting effect more than 10 times that of conventional heat collecting members mainly made of copper. The purpose is to provide heating members.

(Means/effects for solving the problem) In order to achieve the above-mentioned object, in the present invention, five
．． A heat collecting member is provided which is made of aluminum or an aluminum alloy and has a surface that is colored to a Munsell brightness of 0 or less and has a reflectance of 30% or less.

The heat collecting member of the present invention needs to have a surface state that simultaneously satisfies the above two conditions. In the case of a surface state where both of these conditions are not satisfied at the same time, even if sunlight hits the surface, the reflectance will be large;
Therefore, the absorption rate (emissivity) of solar heat is small, and there is no sufficient heat collection effect.

Such a surface state can be formed by applying the following method.

First, for example, the surface of an aluminum or aluminum alloy plate that has been processed into a predetermined shape is roughened by sandblasting, etching with sodium hydroxide, hydrochloric acid, etc., or surface polishing with sandpaper. Make the surface rough.

The degree of roughening may be changed depending on the state of coloring based on the surface coloring treatment described below, but in order to make the surface reflectance 30% or less, Rmax 1000
It is preferable to set it to 100 micrometers. For example, in the case of sandblasting, the degree of surface roughening can be achieved by appropriately selecting conditions such as sand particle size, blasting pressure, and processing time.

Next, the plate-shaped body whose surface has been roughened in this manner is subjected to a coloring treatment, and the surface is colored so that the brightness in the achromatic color array of the Munsell color chart becomes 5.0 or less.

This surface coloring treatment is performed by immersing the plate-like body in hot water, which will be described later.

The hot water used contains carbonate ions and silicate ions.

One or more of sulfate ions, phosphate ions, nitrate ions, and chloride ions are contained.

These anions act on the hydrated oxides formed by this hot water on the surface of aluminum or aluminum alloys, turning them blackish.

If the content of these anions is too small, the above-mentioned effects will not be fully exhibited, and the surface of the aluminum or aluminum alloy after treatment will not have a dark color tone of 5.0 or less on the Munsell scale, and the content will be too low. If it is too large, the problem arises that it actually prevents the formation of water-conserving oxides on the surface of aluminum or aluminum alloy and reduces the coloring effect, so the total content should be between 5 and 200%.
It is preferably about ppm.

,=h As a source of anions, for example, CaCO
3. Carbonates such as BaCO3, Na2COs; Nat
Silicates such as O'SiCh, KxO・SiCh; ZnSO4, FeSO4, CuSO4, CuS
Sulfates like O4; KHzPO4, Na3PO4,
Phosphates such as BaHPO+; Ca(No3)2.
NaNO3, Fe(NO,).

nitrates such as; chlorides such as NaCA, KCI, FeClt; These winter particles may be dissolved in hot water so that each anion has a predetermined concentration. At this time, winter dissociates in hot water, and the generated sodium ions, potassium ions, calcium ions, magnesium ions, iron ions, copper ions, zinc ions, etc. are also good for surface coloring along with each anion. influence

Adding an additive such as aqueous ammonia or triethanolamine to the hot water is effective in reducing the Munsell brightness of the surface. The amount of ammonia water to be added may be, for example, about 0.1 to 1.5% by volume in the case of 28% ammonia water, and about 0.1 to 1.0% by weight in the case of triethanolamine.

Furthermore, it is preferable that the pH of the hot water is adjusted to 7-11. This is because if the pH of the hot water is outside the above range, the time required for surface coloring becomes longer and at the same time, it is difficult to form a dark-toned surface with a Munsell brightness of 5.0 or less.

The temperature of hot water is controlled at 80-100°C. If the temperature of this hot water is lower than 80° C., the time required for coloring becomes long, making it impractical, and the Munsell brightness of the surface after treatment becomes greater than 5.0.

A preferred state of the hot water is a boiling state. At this time, the surface of the treated aluminum or aluminum alloy becomes a dark color with a Munsell brightness of 5.0 or less in a short time.

Furthermore, if the aluminum member is immersed in hot water for too short a time, the surface color change will be insufficient, and if the aluminum member is immersed in hot water for too long, it will only reduce productivity, so the Munsell display brightness should be 5.0. To achieve the following, usually 2
It is sufficient if it is about 10 minutes.

(Embodiments of the Invention) Examples 1 to 8 First, ten aluminum plates measuring 150 mm in length, 100 mm in width, and 2 strokes in thickness were prepared. The surfaces of these aluminum plates are all polished surfaces with an Rmax of 500 μm,
The Munsell brightness was 7°2 in all cases.

Next, both sides of these aluminum plates were subjected to sandblasting under different conditions to create surface conditions with different degrees of roughness.

On the other hand, hot water (pH adjusted to 8.5) in which Na, 0 2 Sin, CaCO5, and triethanolamine were dissolved and the concentrations of the above components differed was boiled (1
00° C.), and each of the aluminum plates described above was immersed therein for 5 minutes to obtain a surface having the Munsell brightness shown in Table 1.

The reflectance and emissivity of each colored aluminum plate were measured based on the specifications below. The results are shown in Table 1.

Reflectance (%) - Measure the ratio of the intensity of the waves reflected at the interface (or number of particles) to the intensity of the incident waves using a reflectometer.

Emissivity (%) Measure the ratio of the radioactivity of a NiAluminum plate (the amount of radiant heat emitted per unit time from unit area) to the radioactivity of a perfect black body surface at the same temperature using an emissivity meter. Therefore, surfaces with higher emissivity absorb more energy. In other words, it indicates that the heat collecting effect is large.

Next, a solar system as shown in FIG. 1 was assembled using each aluminum plate.

That is, a meandering narrow waterway 2 is bored inside the aluminum plate 1 as shown in the figure, and its entrance 2a.

Water pipes 3a and 3b were connected to the outlet 2b, respectively.

These water pipes 3a and 3b are connected to a water tank 4 having a capacity of 1%. The water temperature in the water tank 4 was 20°C.

While the surface of the aluminum plate l is exposed to sunlight, the water tank 4 is activated by operating the pump 5 installed in the water pipe 3a.
The water inside was circulated in the order of water tank 4 -> water pipe 3a -> waterway 2 - water pipe 3b -> water tank 4. This state was continued, and the time required for the temperature of water 1 in water tank 4 to rise from 20°C to 50°C was measured. The results are shown in Table 1.

In addition, without sandblasting, the surface was colored to have a Munsell brightness of 5.0 (reflectance 43%).
), sandblasted to have a reflectance of 26%,
The solar system was assembled in the same manner as in the example for each case whose surface had a Munsell brightness of 6.5 through coloring, and the time required for the temperature of the water IM in the water tank to rise from 20°C to 50°C was calculated. was measured and the results were compared to Comparative Example 1. It is shown in Table 1 as Comparative Example 2.

In addition, the first plate was made of a copper plate having the same dimensions as the aluminum plate in the example.
Assemble the tool run stem as shown in the figure, measure the time required for the temperature of the water tank to rise from 20℃ to 50℃ in the same manner as in the example, and the results are shown in Table 1 as a conventional example. Indicated.

(Margin) Table 1 (Effects of the Invention) As is clear from the above explanation, the heat collecting member of the present invention has the following properties:
Its emissivity is 0.4 or more, which is more than 10 times that of the conventional one, and its heat collecting effect is extremely excellent.

And 1. The time required to raise water from 20°C to 50°C is less than 10 hours, and it can be used as a heat collecting member for general household solar systems.

Furthermore, since the heat collecting member of the present invention is made of aluminum or aluminum alloy, it is lighter than conventional members. Therefore, it is possible to assemble a relatively lightweight large-scale solar system, and it becomes possible to produce a large amount of hot water even in an ordinary household.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a solar system incorporating the heat collecting member of the present invention. 1... Aluminum plate (heat collecting member), 2... Channel, 2a... Channel inlet, 2b... Channel outlet, 3a
, 3b... Water pipe, 4... Water tank, 5... Pump.

Claims (1)

[Claims] A heat collecting member characterized by being made of aluminum or an aluminum member colored to a Munsell brightness of 5.0 or less and having a surface with a reflectance of 30% or less.