Hybrid thermal management of a PCM-based heat sink with radial composite fins under temperature-controlled intermittent forced convection

Most PCM-based heat-sink studies involving forced convection employ continuous fan operation, and it remains unclear how PCM thermal storage and release affect fan operation. To address this gap, a PCM-based thermal management system combining a heat sink with radial composite fins and temperature-controlled intermittent forced convection is proposed to investigate how PCM volume fraction affects fan switching behavior and operating time. Numerical simulations combined with experimental validation examine the thermal response, phase-change behavior, and fan operating characteristics at PCM volume fractions of 0%, 30%, 60%, and 83% under different cooling modes. Under passive cooling, compared with the 0% HS-PCM, the 83% HS-PCM delays the time for T1 to reach the limit temperature of 80 °C by 190.0–1004.2 s at 40–120 W. Under continuous forced convection, PCM volume fraction has little effect on the steady-state temperature of T1. Under temperature-controlled intermittent forced convection at 40 W, compared with the 0% HS-PCM, the temperature-control cycle durations of the 30%, 60%, and 83% HS-PCM are extended by 1119.8, 1900.7, and 2416.3 s, respectively. Over the common evaluation period of 7220.0 s, intermittent operation reduces the fan operating time by 33.2%–41.0% compared with continuous forced convection, while maintaining T1 below 80 °C. These findings clarify how PCM thermal storage and release influence temperature-controlled fan operation.