Fabrication and performance characterization of a phase-change thermal diode using scaly-finned fibers as the wick

Efficient unidirectional heat transfer is of paramount importance in applications such as satellite thermal control systems and large-scale data centers, where conventional phase-change heat transfer devices exhibit inherent limitations. In this study, a novel phase-change thermal diode was proposed for unidirectional and self-driven thermal management. Fiber wick structure featuring periodic oblique scaly fins and unidirectional self-driven liquid transport capability was fabricated via multi-tooth cutting process and high-temperature solid-state sintering method, and was then encapsulated to construct phase-change thermal diodes. The steady-state heat transfer performance, unidirectional heat transfer characteristic, and adverse-gravity capability of the thermal diodes were evaluated by adjusting the filling ratio, heating power, and operating conditions. Experimental results revealed that a lower filling ratio correlated with higher effective thermal conductivity and enhanced unidirectional heat transfer performance, among the tested devices under horizontal operating conditions and filling ratio range of 40% to 60%. Specifically, a maximum thermal rectification coefficient of 0.56 ± 0.03 with the thermal conductivity of 4858 ± 369 W/(m·K) was achieved at a filling ratio of 40%. Under adverse-gravity conditions, the maximum effective thermal conductivity was reduced, and the unidirectional heat transfer capability was retained but weakened at low filling ratios. The tested phase-change thermal diodes exhibit high effective thermal conductivity and appreciable thermal rectification, suggesting potential for advanced thermal management applications.