Performance of an air-cooled heat sink with microscale dimples under transitional flow conditions

The objective of this effort is to pursue artificial microscale surface roughness features in the form of dimples, on the fins of an air cooled heat sink, as a passive option to energy-efficiently augment heat transfer in forced convection flows. High fidelity numerical simulations were employed for realizing an optimized dimple configuration and to comprehend the behavior of micro-sized dimples under high velocity (~17 m/s) transitional flow conditions. Fully developed flow simulations were performed, and design of experiments with response surface methodology was employed for the numerical optimization. The results showed up to 30% heat transfer improvement in the fully developed region compared to a smooth finned channel. Experiments were also carried out to assess the performance of the aforementioned optimized configuration in a custom built setup in the laboratory, which showed up to 10.5% heat transfer improvement over a corresponding smooth-walled channel. The results showed that application-specific optimization of dimples is crucial. With further exploration of shape and design parameters, dimples might have the potential to improve thermal performance passively and form an attractive candidate to realize high-performance air-cooled heat sinks in the future.