Nowadays, more and more people are installing solar water heating systems. Today, we will introduce several vacuum tube solar collectors commonly used in solar water heating systems. How is your evacuated tube solar collector for solar water heating system composed?
The evacuated tube solar collector is a solar collector that uses a glass tube and has a vacuum space between the tube wall and the heat sink. The evacuated tube solar collector also contains all-glass evacuated tube collectors and glass-metal structure evacuated tube collectors. For example, according to the structure of vacuum solar collectors, it can be classified into three categories, namely, all-glass evacuated tube solar collectors, glass-metal structure U-shaped evacuated tube solar collectors, and heat pipe evacuated tube solar collectors.
Different from the flat plate collector, the selective absorption coating of the evacuated tube collector works in a vacuum environment inside the evacuated collector tube, and has good aging resistance and low overall heat loss.
Next, let’s talk about the all-glass evacuated tube solar collector, which is a collector that uses all-glass evacuated tubes as the heat-collecting element. The more common ones are a variety of header collectors and a variety of derivative products by inserting U-shaped tubes or metal heat pipes into the all-glass evacuated collector tubes as heat transfer components.
The manifold collector in the all-glass evacuated tube solar collector is composed of evacuated collector tubes, headers, tailstocks, brackets and other components, and the all-glass evacuated collector is used as the collector component. The manifold connects multiple vacuum tubes together to form a whole. If the water is in the glass tube, the solar radiation will pass through the cover glass tube of the vacuum collector and then be absorbed by the inner glass tube coated with selective absorption coating. , The water in the tube can be directly heated. Generally, the header collector is mainly used for non-pressure systems.
Because the inner tube of the collector tube of the header collector is in direct contact with water, and metal materials such as copper and stainless steel are not used, the cost performance is still quite high, and the glass tube has strong corrosion resistance, so the all-glass vacuum tube collection Heater replacement and maintenance are also relatively convenient and easy, so this collector is suitable for domestic hot water and solar hot water projects. However, the collector is sealed with a silicone ring, which makes it unable to operate under pressure. If a vacuum tube ruptures during operation under pressure, the entire system may be paralyzed. In cities with high water hardness, it is easier to build up scale in the collector tubes and headers, so it needs to be cleaned regularly.
The all-glass evacuated tube U-tube collector uses all-glass evacuated collector tubes as the heat-collecting element, inserts metal U-tubes, and double-layer glass for vacuum insulation. The heat absorber is an inner glass plated with a selective absorption coating. The heat transfer working medium in the metal U-shaped tube is then heated by the heat transfer component. It is an improved type of header collector. It enables the all-glass vacuum heat collector tube to be used and operated in a pressure-bearing system. Improved reliability. Even if some of the glass vacuum heat collection tubes are broken, the internal metal heat transfer working fluid channel will not leak, so that it can still operate normally.
The all-glass evacuated tube heat-pipe collector uses all-glass evacuated heat-collecting tubes as the heat-collecting element, and is also double-glazed for vacuum insulation. The heat sink is an inner glass tube plated with a selective absorption coating, and then passes through the heat transfer component. The evaporation section of the metal heat pipe is heated and the heat is transferred from the metal heat pipe to the condensation section of the metal heat pipe, and then the water or heat transfer working fluid in the header is heated. It can be used in pressure-bearing systems as well as non-pressure-bearing systems, and its performance is relatively reliable. Borrowing from the previous paragraph, even if some of the glass vacuum collector tubes are broken, the internal metal heat transfer working fluid channel will not leak, so that it can still operate normally.
Metal is the heat absorbing body of the glass-metal structure vacuum solar collector tube and the vacuum solar collector tube whose heat transfer medium does not undergo phase change. Similarly, this kind of collector tube is a collector made of collector elements. The glass-metal sealing vacuum belongs to a sealed structure. It is a single-layer glass vacuum tube. The metal absorption strip is used as the heat absorption plate. The U-shaped tube is used as the metal flow channel of the heat absorption body. There are two sealing methods, melt sealing and heat compression sealing.
The heat pipe type vacuum tube means that the heat transfer element of the vacuum tube heat collection tube is a heat pipe. Similarly, the heat pipe vacuum tube heat collector is a heat collector composed of heat pipe vacuum tubes. The glass-metal sealing vacuum is a sealed structure. It is a single-layer glass vacuum tube. The metal absorption strip serves as a heat-absorbing plate. The heat-absorbing body contains a metal heat pipe. The evaporating section of the heat pipe is transferred to the heating and heat transfer working medium of the condensing section, and there are two sealing methods for glass-to-metal, fusion sealing and thermal compression sealing.