Coupled convection–radiation heat transfer and optimization in microscale fin structures

With the increasing power density of electronic devices, effective thermal management is essential for maintaining performance and reliability. Although air-cooled heat sinks have been extensively investigated, studies have primarily focused on structural optimization and convective heat transfer, while the contribution of surface radiation has received comparatively limited attention in microscale thermal management. This study investigates a backside-integrated air-cooled heat sink, with particular emphasis on the coupled effects of forced convection and surface radiation at the microscale. Comparative analysis shows that the parallel plate fin structure provides the best heat dissipation performance, while fin optimization reveals a trade-off between heat transfer enhancement and flow resistance. Furthermore, increasing the inlet velocity effectively enhances convective heat transfer and reduces the chip temperature, but the cooling benefit gradually diminishes beyond approximately 1.2 m/s, whereas flow-related energy consumption continues to increase. Meanwhile, radiative heat transfer is strongly influenced by flow conditions and input power, with surface emissivity playing an increasingly important role under low velocity and high input power conditions. At an inlet velocity of 0.2 m/s, increasing the emissivity from 0.05 to 0.95 reduces the maximum chip temperature by approximately 10.8 °C at 0.1 W and 33.3 °C at 0.3 W. At ε = 0.95 and v = 0.2 m/s, the radiative contribution reaches 32.0%, 34.3%, and 36.4% at input powers of 0.1 W, 0.2 W and 0.3 W, respectively. These results demonstrate that appropriate matching of inlet velocity and surface emissivity can effectively regulate heat dissipation while reducing reliance on excessive airflow. The findings provide a practical basis for the design and optimization of integrated thermal management systems for high power density electronic devices.