Thermal performance improvement of a radial pulsating heat pipe with diverging channels by adopting Tesla valves at various heat fluxes

The thermal performance of a pulsating heat pipe (PHP) can be improved by increasing the flow circulation with the adoption of novel channel designs to minimize flow resistance. This study aimed to improve the thermal performance characteristics of a radial PHP with diverging channels by adopting Tesla valves. The effects of heat flux, condensation temperature, and heat transfer area ratio on the thermal resistance and heat transfer coefficient of the PHP with Tesla valves were measured under different heating and cooling conditions. In addition, the flow behaviors and pressure variations were analyzed for a short time frame. The PHP with Tesla valves exhibited a 17 %-lower thermal resistance than that without Tesla valves owing to the increased flow circulation with preferential movement in one direction. Furthermore, the heat transfer capability of the PHP with Tesla valves increased with increasing condensation temperature and heat transfer area ratio at the same heat flux. In addition, the optimal filling ratios were determined to be 70, 80, and 90 % for heat transfer area ratios of 0.13, 0.08, and 0.05, respectively. Finally, contour maps for the maximum temperature deviation were developed in terms of the heat flux, heat input, and heat transfer area ratio.