Dutch knowledge center for heat pipe technology
Traditionally a heat pipe, as shown in the figure below, is manufactured as a tubular metal structure closed at both ends. It encompasses three essential parts: an evaporator, an adiabatic transport section and a condenser. Inside the heat pipe a working fluid is present both in the liquid and the vapor phases. A heat flux entering the evaporator, for instance from a hot component, vaporizes any available coolant liquid, thereby absorbing large quantities of heat. The vapor, indicated by the red arrows, travels through the adiabatic transport section to the condenser, propelled by the difference in pressure. In the condenser the vapor condenses as the temperature is lower, releasing its latent heat. This heat can be extracted from the heat pipe by a heat sink. To complete the cycle, the condensed liquid must be pumped back to the evaporator, as indicated by the blue arrows. The fluid return is facilitated by a capillary or wick structure, indicated in gray. The wick structure, saturated with the liquid phase of the working fluid, is able to transport the fluid, due to the capillary pressure caused by the difference in curvature of the liquid menisci.