Heat pipes: novel experimental insights into the phenomenological understanding

The present dissertation reports the most meaningful outcomes referred to global and local heat transfer investigations on different Heat Pipe devices, either wicked or wickless. The experimental campaigns have been carried out in the framework of the ESA MAP project TOPDESS (grant 4000128640/19/NL/PG/pt) through fruitful collaborations between the University of Parma and the University of Poitiers (France), the University of Pisa (Italy), the University of Brighton (United Kingdom) and the Federal University of Santa Catarina (Brazil). The newly proposed post-processing methods, which allow the estimation of thermofluidic interactions due to inner convection, are based on infrared acquisitions on the outer wall of the investigated systems. The non-intrusive feature of such techniques strongly enhances their applicative appeal in terms of experimentation since no substantial alterations of the original layouts are required. By a systematic data reduction of the evaluated quantities, which also relies on statistical approaches, interesting thermo-fluid dynamic patterns have been identified. Despite the studied devices present different geometries and thermal performances, their local behaviours have been proven to be linked by a common thread. The provided remarks are of crucial importance for the phenomenological understanding of two-phase passive heat transfer devices working under highly transient conditions. Moreover, they set the basis for the improvement and proper validation of existing numerical models, opening to reliable designing approaches and consequent large-scale applications of modern and still immature thermal management solutions. Future works are needed to fully characterize the local heat transfer in a wide range of devices and working conditions.