Thermal management performance of intermittent high-power airborne electronic equipment using N-pentadecane/expanded graphite composite phase change material

Airborne high-power electronic devices often experience pulsed heat loads with high peaks, short durations, and periodic fluctuations. Designing a vapor compression refrigeration system solely for peak loads increases system size and weight, whereas average-load design cannot ensure transient temperature control. To address this trade-off, this study proposes a lightweight-oriented active thermal management method that couples a vapor compression refrigeration system with a form-stable n -pentadecane/expanded graphite (PA/EG) phase-change buffer unit. The unit is inserted between the heat source and evaporator, where it absorbs transient heat during high-load periods and is cooled by the evaporator during low-load periods to restore heat-storage capacity. PA/EG composites were prepared by vacuum impregnation and compression molding, and the effects of EG content and compacted density on thermal conductivity, latent heat, leakage behavior, and cycling stability were examined. The porous EG skeleton provided PA adsorption/encapsulation and continuous heat-conduction pathways. PA/EG-40 wt% reached a thermal conductivity of 16.8 W·m −1 ·k −1 , corresponding to an approximately 105-fold increase over pure PA, while molten leakage was effectively suppressed when the EG content was at least 10 wt%. Considering heat conduction, latent heat retention, shape stability, and the mass penalty of EG loading, PA/EG-10 wt%-0.9 g·cm −3 was selected and maintained stable temperature responses after 200 melting/solidification cycles. Under a 60 W cooling capacity and 150 W/15 W pulsed heat load, the coupled unit reduced the peak heat-source temperature from 45.3 °C to 29.5 °C. This work provides a feasible phase-change buffering strategy for lightweight active thermal management of intermittent high-power electronics.