Composition and product differences of solar vacuum tubes：
Ordinary all-glass vacuum tube consists of seven parts:
Outer glass tube, inner glass tube, selective absorption coating, vacuum sandwich, getter, getter film, spring clip.
(1) The solar vacuum tubes used in household solar water heaters are divided into 37, 47, 58 and 70 mm in diameter and 1.2, 1.5, 1.6, 1.8, 2.1 and 2.3 m in length.
(2) According to the production process, it can be divided into solar common black tube, ordinary blue tube, three high blue tube and three high purple gold tube.
The difference between three high "solar core" vacuum tubes and ordinary tubes is that the endothermic film layer is different (endothermic film is the key part of the vacuum tube). The three-higher pipes are interference film and the common tube is gradual film. The main difference between them is the difference between the interference film and the gradient film.
1. Fundamental difference: Different film structures lead to different principles of absorbing sunlight. Gradient film is a multi-layer film. Its absorption layer is usually 9 layers. It absorbs solar light layer by layer, and its absorption performance is gradually improved. As a result of this gradual structure, the emission ratio increases with the increase of temperature, so that the emission ratio increases greatly when the working temperature is 300 ~ 500 ℃. In addition, the activity of Al ions in the absorption layer is greatly enhanced and drift occurs at high temperature. In this way, the internal structure of the film is disordered, which leads to the aging of the film. In this high temperature condition for a long time, the film will fall off, thus affecting the collection efficiency and life of the vacuum tube.
The interference film consists of two absorption layers. The interference between the two layers is caused by the different proportion of metal components, which increases the absorption ratio and decreases the emission ratio. In addition, the anti-reflection layer reduces the reflection, so as to achieve higher absorption ratio and lower emission ratio, which greatly improves the collection efficiency.
2. Characteristic: The absorption ratio of the three-high pipes increased by 12%, the emission ratio decreased by 30%-40%, the super absorption, less heat loss and faster heating. High efficiency tube, super absorption, high thermal efficiency, fast heating, under the same light conditions, more and higher water temperature hot water can be produced than ordinary tube; Alpine tube, because the emission of copper ions is 0.2 lower than that of aluminum ions, so heat loss is very small, it can still work normally in high-cold environment, - 30℃ hot water; High temperature special effect tube, because the stainless steel ions in the film are resistant to high temperature, air and sunshine, film layer. No ageing, no fading and no color change at 400 ℃.
Under the same illumination conditions, the heat absorption of ordinary pipes is not as high as that of three-higher pipes, or even can not meet the requirements of bathing; when the temperature is low, the heat loss is greater, the heat collection efficiency decreases, affecting the normal use; especially when the air temperature exceeds 270 ℃, the film begins to aging and fall off, the absorption rate decreases rapidly, and the service life is greatly shortened.
3. Technology: Three-target, double-target and single-target magnetron sputtering technology is used for high temperature special effect tube, high-cold tube and high efficiency tube respectively; single-target magnetron sputtering technology is generally used for common tube.
4. Appearance: A, the orifice, where the film is sealed at high temperatures above 800 ℃ part of the shedding is inevitable. Because of high temperature resistance, the high temperature special effect tube is only about 1 centimeter long without film, while the other tubes are not high temperature resistant, the film shedding length is about 2.5 centimeters. B, Inner tube color: Observed by naked eyes, the inner tube color of high temperature and high temperature pipes is dark red (because the bottom layer of the film is copper), while the high efficiency pipes and ordinary pipes are white (because the bottom layer of the film is aluminum).