Numerical investigation on the heat transfer characteristics and dynamic adaptability of cascaded phase change material (PCM) heat sinks under flight conditions

Efficient thermal management of airborne electronics is critical for aerospace missions involving high maneuverability and power density. While cascaded phase change materials (PCMs) show theoretical promise, existing research is largely confined to static ground conditions, leaving their physical mechanisms under dynamic flight environments unexplored. A custom-coded three-dimensional (3D) distributed parameter numerical model was developed to systematically investigate the heat transfer and dynamic adaptability of cascaded PCM sinks across all flight inclinations (0–180°) and accelerations (0.1g–9g). A multi-level synchronous melting mechanism was identified in the cascaded structure under conduction-dominated regimes, fundamentally different from the top-down unidirectional melting in single-stage PCMs, which extended the thermal management time by 39.9 %. The cascaded heat sink was found to exhibit remarkable dynamic stability under varying flight conditions, with a temperature response shift below 5 % and a performance variation of only 1.84 % across all tested conditions, demonstrating that the cascaded structure effectively mitigates performance fluctuations induced by acceleration and inclination. A performance reversal was observed as the inclination decreased from 135° to 0° and the acceleration increased from 0.1g to 9g. Under these strong convection regimes, the single-stage configuration outperformed the cascaded design due to the latter's lower total enthalpy and the structural damping of large-scale Rayleigh-Bénard circulation. The novelty lies in the revelation of the multi-level synchronous melting mechanism and dynamic adaptability of cascaded PCM heat sinks under flight conditions, along with the elucidation of the performance reversal triggered by the trade-off between the cascaded design and the material's energy storage capacity. The findings provide theoretical criteria for mission-oriented design: cascaded structures are optimal for dynamic adaptability in maneuvering flights, while single-stage sinks are favored for strong-convection environments.