**Author details**

**6.4. Effective thermal conductivity**

370 Bringing Thermoelectricity into Reality

**7. Conclusions**

**Acknowledgements**

**Nomenclature**

*AC* cross-sectional area, [m2

*Di* inner diameter, [m]

*I* current, [A]

increases with increasing power dissipation.

conductivity, on the other hand, a solid rod cannot be used.

In **Figure 19**, the behavior of the effective thermal conductivity of the passive heat transfer devices is shown as a function of the power dissipated for vertical (a) and horizontal (b) positions. As expected, it can be seen that the passive devices that use phase change (heat pipes and thermosyphon) have a higher effective thermal conductivity and that this parameter

In this research, each step of the heat pipes and the thermosyphon manufacturing (cleaning, assembly, tightness test, evacuation procedure, and filling with the working fluid) was described in detail. The proposed procedure has low-cost and the heat transfer passive devices are easy-to-manufacture. Then, an experimental investigation of the thermal performance of different heat transfer passive devices (solid rod, thermosyphon, mesh heat pipe, grooved heat pipe, and sintered heat pipe) was performed. These passive heat transfer devices were tested in vertical and horizontal positions under thermal loads between 5 and 45 W and worked satisfactorily, except rod and thermosyphon in the horizontal position. The vertical position showed better results than the horizontal one due to gravity. The thermosyphon showed a satisfactory thermal performance in the vertical position. However, in the horizontal, its behavior was worse than a rod. The heat pipes were the devices with the best thermal performance due to the use of the vaporization heat of the working fluid concurrently with the capillary structure. The grooved heat pipe had a better thermal performance based on the lower global thermal resistance or the higher effective thermal conductivity. The experimental results showed that heat pipes and thermosyphon can be successfully used in TEC hot side cooling, and due to the behavior of the global thermal resistance and the effective thermal

Acknowledgments are provided to the CAPES, the CNPq, the PROPPG/UTFPR, the DIRPPG/

UTFPR, the PPGEM/UTFPR/Ponta Grossa, and the DAMEC/UTFPR/Ponta Grossa.

]

Thiago Antonini Alves\*, Larissa Krambeck and Paulo H. Dias dos Santos

\*Address all correspondence to: thiagoaalves@utfpr.edu.br

Federal University of Technology, Parana, Brazil
