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. This tube is widely used in the mild place of the world for its high quality and competitive price.The heat pipe series solar collector are always connected with existing heating supply device. The selective coating on the inner cover of the evacuated tubes converts solar energy into heat energy and transfers heat to the heat pipes by aluminium fins. The liquid in the heat pipe changes into vapour which rises to the condenser. The heat then passes through the heat exchanger and the vapour becomes liquid, returning to the base of the heat pipe. The heat conducts to the heat transfer liquid (anti-freezing liquid or water) via a copper pipe. This transference of heat into the liquid creates a continuous circulation as long as the collector is heated by the sun
