Análise experimental do desempenho térmico de termossifões e tubos de calor contendo nanofluido de óxido de grafeno

Abstract

Thermosyphons and heat pipes are passive devices able to transfer large amounts of heat through the latent heat of vaporization of a working fluid. Nanofluids are presented as a new generation of heat transfer fluids due to the improvement of thermophysical properties. Given these circumstances, in the present Work of Conclusion Course, an experimental analysis of the thermal performance of thermosyphons and heat pipes was performed using graphene oxide nanofluid, in volumetric concentrations of 5.0% and 2.5%, as working fluid. For the geometric characteristics of the enclosures, they were built in copper, with an outer diameter of 9.45mm, an inner diameter of 7.75mm, and a total length of 200mm, and, for the heat pipe, the capillary structure was made by phosphor bronze #130 wire mesh. The experimental tests were done at two different inclinations (45 and 90° in relation to the horizontal), under thermal loads from 5 to 45W and with forced convection in the condenser. The results showed that the use of graphene oxide nanofluid reduced considerably the thermal resistance and the operating temperature of the thermosyphon, when compared to the use of distilled water as a working fluid, furthermore, the volumetric concentration of 2.5% presented the best results among the analyzed working fluids. However, for the heat pipe with wire mesh, the use of graphene oxide nanofluid was not efficient, was observed an increase in thermal resistance compared to distilled water. This worsening in the thermal performance of the heat pipe was attributed to incrustations of agglomerates of graphene oxide nanoparticles in the capillary structure, which made difficult for the liquid to return to the evaporator.