ABSTRACT
This chapter explores various phenomena associated with heat pipe operation, and explains their influence on heat pipe operational characteristics. Capillarity refers to the capability of the interface between a liquid and a gas or vapor in a fine-pored structure to withstand a pressure difference across the interface. Capillarity plays an essential role in the transport of heat through heat pipes by providing the mechanism for automatic recirculation of the heat pipe fluid. In a heat pipe, since capillarity is responsible for circulation of the heat pipe fluid, strongly wetting or nonwetting liquids are preferred. The capillarity of the wick in a heat pipe is a major factor in establishing heat transport capability. In a properly designed heat pipe the actual heat transport rate will then be a relatively small fraction of the sonic limit, and the heat pipe will be virtually isothermal.
