A typical heat pipe consists of a tube shell, a wick and an end cap. The inside of the tube is pumped to a negative pressure of 1.3×(10-1~10-4 ) Pa and then filled with an appropriate amount of working fluid. The capillary porous material close to the inner wall of the tube is filled with liquid and then sealed. One end of the tube is the evaporation section (heating section), and the other end is the condensation section (cooling section). According to the application needs, an adiabatic section can be arranged between the two sections. When one end of the heat pipe is heated, the liquid in the wool wick evaporates and vaporizes, and the steam flows to the other end under a slight pressure difference, releasing heat and condensing into a liquid. The liquid flows back to the evaporation section along the porous material by capillary force. In this way, the heat is transferred from one end of the heat pipe to the other end. In the process of realizing this heat transfer, the heat pipe includes the following six interrelated main processes:
⑴ Heat is transferred from the heat source to the (liquid-vapor) interface through the heat pipe wall and the wick filled with working liquid;
⑵ The liquid evaporates on the (liquid-vapor) interface in the evaporation section;
⑶ The steam in the steam chamber flows from the evaporation section to the condensation section;
⑷ Steam in the condensation section. Condensation on the liquid interface:
⑸ Heat is transferred from the (vapor-liquid) interface to the cold source through the wick, liquid and tube wall;
⑹ The condensed working liquid flows back to the evaporation section due to capillary action in the wick.
