Thermosyphons are passive heat exchanger devices that use the latent heat of vaporization of a working fluid to intensify heat transfer. They consist of a metallic tube, passed through a vacuum process, and filled with a working fluid, and use the action of gravity to circulate the fluid internally. They are used to enhance heat transfer in many industrial areas, such as aerospace, electronics, and telecommunications, among others. In the literature, several studies are related to the subject under study, both experimental and numerical analyses. Still, there isn’t validation of the results, especially when obtaining the boiling heat transfer coefficient. Thus, the main objective of the present work consists of determining an experimental test bench, from Dirichlet’s Condition, varying an evaporator wall temperature (303.15, 313.15, and 323.15K) and water filling ratio (50 and 100% of the evaporator’s volume) into stainless-steel thermosyphon, providing experimental data for validation of numerical simulations carried out using the Ansys® FluentTM software. The comparison between numerical and experimental results demonstrated good agreement validating the numerical methodology.