Heat Pipe Components and Materials

This chapter discusses the main components of the heat pipe and the materials used. The issue of compatibility and the results of life tests on heat pipes and thermosyphons remain critical aspects of heat pipe design and manufacture. The three basic components of a heat pipe are: the working fluid, the wick or capillary structure, and the container. In the selection of a suitable combination of these components, a number of conflicting factors may arise. A first consideration in the identification of a suitable working fluid is the operating vapor temperature range and a selection of fluids. The selection of the wick for a heat pipe depends on many factors, several of which are closely linked to the properties of the working fluid. The prime purpose of the wick is to generate capillary pressure to transport the working fluid from the condenser to the evaporator and to distribute the liquid around the evaporator section to any areas where heat is likely to be received by the heat pipe. The function of the container is to isolate the working fluid from the outside environment. It has, therefore, to be leak-proof, to maintain the pressure differential across its walls and to enable the transfer of heat to take place into and from the working fluid.