Theoretical and experimental analyses of the thermal resistance of a loop thermosyphon for passive solar heating of buildings

This study presents experimental and theoretical analyses of the thermal performance of a two-phase copper-R141b loopthermosyphon, which was developed for solar heating of buildings. A prototype of the so-called wall-thermosyphon was built and tested at the Heat Pipe Laboratory of the Federal University of Santa Catarina (Labtucal-UFSC). During the tests, three parameters were varied: purge method, power input levels and inside wall evaporator roughness. The results show that recent boiling heat transfer coefficient literature correlations is in good agreement with the experimental data for the thermal resistance of the device under study. However, the condensation thermal resistance calculated with the literature correlations do not represent the same trend found in the experiments. The total thermal resistance of the wall-thermosyphon varies between 0.22 and 0.011 °C/W.