Study of an annular two-phase thermosyphon used as an isothermal source in thermometry

The feasibility of using an annular two-phase thermosyphon (TPT) in thermometry was studied experimentally; the main results are presented in this paper. The TPT was conceived as an isothermal source for calibration purposes, using the comparison method. For this purpose, an annular TPT was designed, built and characterized, using water as a working fluid. In order to determine experimentally how isothermal the TPT annular surface can be, eight thermocouples were installed axially on its surface. Tests were performed for two different cooling water flows 16.67 cm³/s and 4.17 cm³/s. For each cooling water flow, four heat power levels were supplied in the evaporation zone: (38, 154, 350, 1,385) W. The experimental results have shown that the thermal device works isothermal for power levels higher than 350 W, where the so-called bar effect is not present and the temperature measurement error is reduced.