The heat pipe and thermosyphon are passive heat transfer devices with phase change, which can be applied for thermal management of thermoelectric cooling, such as the TEC hot side. The heat pipes basically consist of a metal tube sealed with capillary structure internally that is embedded with a working fluid. This capillary structure can be made of screen meshes, grooves, or sintered media. The thermosyphon is a heat pipe assisted by gravity, because it has no capillary structure. Then, in this chapter, manufacturing of low cost and easy-to-manufacture heat pipes and thermosyphon is described in detail, and an experimental evaluation of their thermal performance is accomplished. The considered devices were a rod, a thermosyphon, a mesh heat pipe, a grooved heat pipe, and a sintered heat pipe. According to the behavior of the global thermal resistance and the effective thermal conductivity, the passive devices operated satisfactorily with the exception of the rod and the thermosyphon in the horizontal position. The heat pipes were the best among the tested devices and the best position was vertical.

The advent of modern electronic technology lead to miniaturization and high power density of electronic devices, then the existing electronic cooling techniques cannot be used, directly affecting the performance, cost, and reliability of electronic devices. Thus, the thermal management of electronic packaging has become a key technique in many products. Passive heat transfer devices can be a good alternative to the stabilization of electronic devices temperature. In this research, an experimental evaluation of the thermal performance of four different passive devices was accomplished. The considered devices were a rod, a thermosyphon, a heat pipe with a metal screen as the capillary structure, and a heat pipe with microgrooves. The heat pipe is a highly efficient device that carries large amounts of power with a small temperature difference. The heat pipe consists of the involucre, the working fluid, and the capillary structure. The thermosyphon is a kind of heat pipe assisted by gravity. In other words, it has no wick structure to return the working fluid. The devices were made of copper with a total length of 200 mm and an outer diameter of 9.45 mm. The thermosyphon and the heat pipes used deionized water as working fluid with a filling ratio of 60% of the evaporator volume. The devices were tested in vertical and horizontal positions under thermal loads between 5 W and 45 W. All the devices have operated satisfactorily when tested in accordance with the behavior of the thermal resistance. The heat pipes were the best among the tested devices and the best position was vertical.

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This paper presents an experimental study on three different capillary structure technologies of heat pipes for application in the thermal management of electronic packaging. The first capillary structure is that of axial grooves manufactured by wire electrical discharge machining (wire-EDM). The sintering process with copper powder produced the second heat pipe. Finally, a hybrid heat pipe was made by the combination of the two previous methods. The heat pipes were produced using copper tubes with an outer diameter of 9.45 mm and a length of 200 mm, and were tested horizontally at increasing heat loads varying from 5 to 35 W. The working fluid used was distilled water. The experimental results showed that all capillary structures for heat pipes worked successfully, so the studied manufacturing methods are suitable. Nonetheless, the hybrid heat pipe is the best, due to the lowest thermal resistance presented.

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