Experimental investigation on melting enhancement of organic phase change materials: Effects of mechanical stirring and water-assisted filling

Rising thermal loads in modern avionic systems have posed critical challenges to conventional cooling technologies. Solid-liquid phase change cooling exhibits great potential in airborne thermal management, but its engineering application is severely restricted by the low thermal conductivity of organic phase change materials (PCMs); existing static enhancement methods cannot fully exploit the convective heat transfer potential during melting, and systematic studies on dynamic enhancement remain insufficient. In this work, the melting enhancement of organic PCMs via mechanical stirring combined with water-assisted filling is investigated, and the effects of key parameters on melting performance are quantified, to provide experimental support for the design of airborne PCM cooling systems. A visualized experimental platform is established. Three n-alkane PCMs with different melting points are selected as test materials, and parametric experiments are carried out under 0–1600 RPM stirring speeds, three filling modes and 8.5–25.5 kW/m 2 heat fluxes, with multiple thermal performance indicators systematically measured. The results show that mechanical stirring significantly improves PCM melting performance, and 800 RPM is identified as the optimal operating speed considering both enhancement effect and energy consumption. The 200 mL water addition mode achieves the most remarkable synergistic enhancement, with the maximum wall temperature drop reaching 30 °C. Lower-melting-point PCMs gain more significant performance improvement under the stirring-water coupling, while rising heat flux notably reduces the stable temperature holding duration. This study provides experimental basis for the parameter optimization of PCM-based thermal management systems for airborne electronic devices.