▎ 摘　　要

Hybrid cooling systems combining forced convection with passive phase change material (PCM) based heat sink is an ideal solution for long-term cooling of high power electronics. The effectiveness of composite PCM with graphene nanofillers on transient performance of a hybrid thermal control system was investigated experimentally under uniform and periodic pulsed heat loads. Graphene was synthesized by liquid-phase exfoliation and paraffin/graphene composite was prepared for various concentrations. The thermo-physical properties of paraffin/graphene composite were measured. Transient thermal responses of heat sink with paraffin/graphene composite (HS-Gr/PCM) and paraffin (HS-PCM) were compared to heat sink without paraffin (HS) for passive and hybrid cooling mode configurations. The thermal performance of HS-Gr/PCM was far superior to HS and HSPCM in all thermal loading scenarios. In passive mode, maximum of 6 degrees C lower steady-state temperature was attained for HS-Gr/PCM relative to HS under uniform thermal load. In hybrid mode, time to reach fan onset temperature was enhanced by 109%, 122% and 110% for HS-Gr/PCM over HS, corresponding to periodic heat pulses with duty factors 0.5, 0.79 and 0.9 respectively. Experiments with hybrid cooling system showed 11-23% enhancement in fan energy savings for HS-Gr/PCM as compared to HS at different periodic heat pulses.