The heat pipe is a metal pipe constructed of a lattice of sealed capillary tubes that contain a very small amount of water. When one end of the pipe is heated, the coolant moves to the cooler end of the pipe where the liquid cools and condenses. The condensation is pushed pack to the heated end of the pipe by the super heated water behind it. This cycle from heating > evaporation > condensation and re-heating sets up a convection current from the front end of the pipe to the rear.
[A] | The end of the pipe where hot paper touches it brings water to boil. |
[B] | Because the small amount of water is sealed in vacuum, the boiling point is very low. |
[C] | Due to the small difference in pressure caused by the heat at the front, the coolant flows from the front to the rear. |
[D] | The coolant condenses and heat the is lost through the surface of the pipe and into the fins at the back. |
[E] | The coolant is pushed from rear to front by the super heated water and steam behind it and the cycle repeats. |