**5. Conclusion**

The methodologies for the calculation of three key parameters implemented in the design and manufacture of two-phase thermosyphons were developed. These key parameters are: the relationship of the lengths of evaporation and condensation zones, the operational pressure values and the evaporation rate of the working fluid during the filling process. The developed methodologies were applied in the design and manufacture of several two-phase thermosyphons. Distilled water was used as working fluid and hydrazine hydrate was added to it as corrosion inhibitor.

Two experimental installations were designed and constructed. One was used to load the thermosyphons, without using a vacuum pump, eliminating the non-condensing gases; the other one is a wind tunnel modified to test the performance of the thermosyphons using electrical resistances as heat source. A series of experiments to investigate the effect of parameters as heat power supply, amount of working fluid and speed of cooling air, on the performance of two-phase thermosyphons were carried out. In each experimental test, the temperature distribution along the external surface of thermosyphons, the heat power supply and the dissipated heat power by the device as well were registered. The results showed that the thermosyphons work isothermally with efficiencies around 90% for a working fluid loading of 20% of the internal volume of the thermosyphon.

The results of these investigations can be used to design and construct high efficiency twophase thermosyphons for heat recovery from waste gas with a temperature up to 250 ºC.
