3. Heat-pipe tube

Heat pipe series solar water heaters are all-glass evacuated solar domestic water systems combined with heat pipes inside the glass tube. The selective coating on the inner tube converts solar energy into heat energy and transfers to the heat pipe by an aluminum fin. The liquid in the heat pipe changes into vapour which rises to the condenser. There is no water in the vacuum tubes,so there will be no water leavings in tube at all ,which avoids clean work and can't lower the heat efficiency after years of use. Even in cold winter it can't be frozen.
The heat conducts the water inside the tank and the vapour becomes liquid, returning to the base of the heat pipe. This continuous circulation transfers heat from the heat pipe to the cold water in the tank as long as sun is heating the collectors. Hot water can be obtained by injecting cold water from the bottom of the tank.

Features:

Some advantage compare with compact solar water heaters.

The system will still operate in the event of occasional tube breakages; Can operate with water pressure up to 0.4MPa;
No additional device for automatic filling water to the tank;
More pressure, more comfortable;

4.U type heat pipe

This kind of tube is like the evacuated heat pipe.Only the copper pipe inside is the U type copper.