Design and performance of a hybrid thermosyphon heat pipe for simultaneous heat transfer and energy harvesting

Thermosyphon heat pipes (THPs) are highly effective devices for transferring heat between a source and a sink. This research presents an innovative method for converting waste heat into electrical energy by incorporating an oscillating magnet within a THP, forming a hybrid thermosyphon heat pipe (HTHP) system. The shape of the oscillating magnet significantly influences both the energy harvesting capability and thermal performance of the system. To investigate this, four magnet geometries—disk, cone, donut, and slippery—with equal mass were tested under increasing heat input until dry-out occurred. Results showed that higher filling ratios not only postponed dry-out but also improved the combined thermal and electrical efficiency of the system. A newly developed dimensionless thermal-electric index was utilized to assess the overall performance of each magnet design. At filling ratios of 10% and 30%, the cone and disk magnets, respectively, exhibited the highest thermal-electric performance. The system demonstrated impressive outputs, including a maximum peak-to-peak open circuit voltage of 1.31 V, an average peak-to-peak voltage of 0.71 V, an RMS voltage of 0.081 V, and a peak electrical power generation of 3.4 mW. These findings underscore the potential of the HTHP system as an effective solution for waste heat recovery and electricity generation.