Composition and Principle of Solar Vacuum Tube
Solar vacuum tube is the core component of solar water heater, known as the "heart" of solar water heater. The quality of vacuum tube directly affects the service life and performance of solar water heater. The rapid development of solar energy industry has also led to the development of vacuum tube enterprises. On the one hand, the patented technology of vacuum tubes has been continuously promoted. On the other hand, the quality of vacuum tubes directly affects the service life and performance of solar water heaters. On the one hand, vacuum tube enterprises and production lines have developed rapidly in recent years. Chinese style Vacuum tube is the core of solar water heater. Its structure is like a slender thermos bottle, with a vacuum between the inner and outer layers. Special technology is used to coat the inner surface of glass tube with spectral selective absorption coating to absorb solar radiation energy to the maximum extent. When the sun shines, the photons hit the coating, and the solar energy is converted into heat energy. Water absorbs heat from coating, water temperature increases, water density decreases, hot water moves upward, and the proportion of cold water decreases. Hot water is always at the top of the tank. The temperature rise of hot water in solar water heater has nothing to do with the outside temperature, but mainly depends on the light. When the faucet of the kitchen or bathroom is turned on, the hot water in the water heater drips out naturally. The larger the drop, the higher the water pressure. At present, the main domestic enterprises producing capitals are Luno, Yuansheng, Huihui and other enterprises. Vacuum tube manufacturing enterprises mainly include Renault new materials, Baoguang collector and other enterprises. There are two main types of enterprises. One is that water does not flow in the pipe, the other is that water enters the pipe. The traditional vacuum tube runs in the tube. Glass is made by double vacuum and "heat pipe direct insertion" vacuum tube. There is no water in the glass tube. As the heart of solar water heater, the Chinese style vacuum tube will change with the change of environment. Because of the difference of region, target consumer group and building, it is necessary for solar water heater to adapt to local conditions and integrate with building effectively.
Solar Vacuum Tube Structure:
The structure of all glass vacuum tube consists of inner glass tube, solar selective absorption coating, vacuum sandwich, cover glass tube, support (spring clamp), getter and so on.
1. The inner glass tube is used as a flow pipe.
2. By means of vacuum deposition, sputtering and electrochemical treatment, the outer surface of the inner glass tube is evenly covered with selective solar absorbing coatings such as copper oxide, black nickel, black chromium, black zinc and black copper to absorb solar radiation energy.
3. Seal the inner glass tube coated with selective coating in the cover glass, then vacuum the inner glass tube and the outer glass tube to form a vacuum sandwich with a vacuum of 0.05 pa, so as to reduce the heat loss caused by air convection and conduction, which is similar to the principle of hot water bottle.
4. All glass vacuum collector tubes are designed with single-ended openings and one end is sealed with inner and outer annular seals. The other end of the tube is a closed hemispherical head. The spring clamp is used to support the round end of the glass tube with cover. When the solar radiation is absorbed in the glass tube and the temperature rises, the glass round end forms a free end of thermal expansion, thus buffering the work of the water heater and generating thermal stress at the open end of the vacuum collector tube.
Composition of Solar Vacuum Tube
Ordinary all-glass vacuum tube consists of seven parts:Outer glass tube, inner glass tube and selective absorption coating, vacuum sandwich and aspirant inhalation film, spring clamp.