The Operating Temperature Of Solar Collectors
Solar collectors are devices that, in the solar heating system, receive radiant energy from the sun and transmit heat to the heat transfer fluid. Solar Collector It is a part of the solar thermal system that is a key component in determining the performance of solar thermal systems.
Classification of solar collectors
With the development of electronic technology, the type of solar collectors more and more diversified. According to whether the direction of solar radiation entering the lighting port is changed, it is divided into a condenser type collector and a non-concentrating type collector. According to the heat transfer type of the collector, it is divided into liquid type collector, air According to whether the collector has a vacuum space, it is divided into a flat type collector and a vacuum tube type collector. According to whether or not the collector is tracking the sun, it is divided into a tracking collector and a non-tracking collector. According to the collector's operating temperature range, divided into high-temperature collector, the temperature collector, low-temperature collector. One of the most common is the solar collectors are divided into flat-type solar collectors and vacuum tube solar collectors.
2.1 flat type solar collectors
Flat type solar collectors are the basic devices of solar low temperature heat utilization. Flat-type solar collectors mainly by the heat-absorbing body, transparent cover, Solar Collector shell and insulation layer and other components. Its structure is shown in Figure 1.
Flat solar collector is the use of solar radiation through the transparent cover, Solar Collector projected on the heat absorber, most of which solar radiation can be absorbed by the heat absorber and converted into heat, and then heat transfer to the heat of the body Heat transfer working fluid. In this way, the heat transfer material is heated, the temperature gradually increased, as a useful heat collector output. Solar Collector At the same time, due to the temperature rise in the heat-absorbing body, through the transparent cover and the shell to the surrounding environment to lose heat, a flat-type solar collectors of various heat loss.
2.2 vacuum tube type solar collectors
Vacuum tube type solar collector is a flat type solar collector developed on the basis of a new collector device. According to the material classification of the heat absorber, can be divided into glass heat absorber vacuum tube (or all glass vacuum tube) collector and metal heat absorber (glass - metal) vacuum tube collector two categories. Mainly all-glass vacuum tube collector, U-tube vacuum tube collector, heat pipe vacuum tube collector.
2.2.1 all-glass vacuum tube collector
All glass vacuum tube collector is a number of all-glass vacuum solar collector tube in accordance with certain rules arranged, and with the reflector, the joint tube and tailstock assembled into a solar collector. All glass vacuum solar collector tube mainly by the inside and outside the glass tube, selective absorption coating, vacuum sandwich, protective cap, getter and other components. Its structure is shown in Figure 2.
All glass vacuum solar collector tube works simple, like elongated thermos. And the inner end of the inner glass tube is closed into a hemispherical round head, Solar Collector and the inner glass tube is supported by the inner end of the outer glass tube with a spring bracket. When the inner glass tube absorbs the solar radiation to heat up, the round head forms the free end of the thermal expansion and contraction, so the buffer causes the thermal stress at the open end of the tube. Inside the glass tube with water, the inner surface of the glass tube coated with sun selective absorption coating, used to absorb solar radiation energy. Will be inside and outside the glass tube between the sandwich into a high vacuum, reduce heat loss, play the role of insulation. Solar Collector A metal protective cap is attached to the end of the outer glass tube to protect the exhausted airtight after evacuation. The spring holder is equipped with a getter that absorbs the gas released during operation of the vacuum heat collector to maintain the vacuum in the tube.
2.2.2 U-tube vacuum tube collector
U-tube vacuum collectors are improved for all-glass vacuum tube collectors. U-tube vacuum solar collector tube structure shown in Figure 3, by the header, Solar Collector heat insulation materials, heat collection fluid, heat pipe U-tube and other components. U-tube vacuum solar collector tube is installed in a vacuum glass tube U-shaped copper tube, vacuum tube to absorb solar radiation energy, through the U-tube flow of refrigerant in the heat transfer to achieve the principle of heating hot water. Solar Collector Because there is no water in the vacuum tube, it will not be damaged due to a tube and affect the operation of the entire system; vacuum tube heat capacity greatly reduced, the same weather conditions can get more heat, thus improving product performance and operational reliability The