How does a thermosiphon evacuated tube solar water heater work?
All-glass evacuated tubes are the key component of solar collectors. The evacuated tube is similar to a conventional Dewar flask and consists of two borosilicate glass tubes, a glass with high chemical and thermal shock resistance. The outer side of the inner tube is coated with a sputtered solar selective surface. This coated inner tube is closed at one end and sealed at the other end to the outer tube. The annular space between the outer tube and inner tube is evacuated to virtually eliminate heat loss by conduction and convection. As the specific gravities of hot water and cold water are different, cold water goes downward and hot water goes upward. When cold water in evacuated tubes is heated, it became lighter and goes to the water tank, while cold water in the tank goes down to the evacuated tubes. Through this circulation, the cold water in the water tank will be gradually heated.
