16 Heat Pipes

A heat pipe is a self-contained closed system that transfers heat through boiling and condensation. The heat pipe is a passive device that provides a means to transfer large amounts of heat with relatively small temperature gradients from a single source or multiple sources to heat sinks. However, heat pipes alone cannot cool equipment. In fact, effective cooling of the condenser section of a heat pipe is required to maintain proper heat pipe performance.

A similar device is known as a two-phase thermosyphon. It has the same basic heat transfer mechanism as a heat pipe, but an important difference exists in the mechanism of condensate return in these devices. A heat pipe relies on the capillary action of an internal wick and a working fluid, whereas a thermosyphon employs an external force field such as gravity or centrifugal force for condensate return to the evaporator. Since there is no wick involved, a two-phase thermosyphon is often referred to as a wickless heat pipe.