Abstract
The boosting heat generation rate of high-performance processors is challenging the conventional cooling techniques. Passive surface structure designs no longer satisfy the heat dissipation requirement. The present work proposes the combined design of active jet intermittency and passive surface modification in heat sinks, and evaluates the heat transfer enhancement through numerical and experimental approaches. The trapezoidal-waveform flow rate at the inlet has constant time-averaged Reynolds number of 763 and the Strouhal number ranges from 0.01 to 0.04. The surface geometry includes cylindrical groove and hemispherical dimple with different arrangements. The underlying physics of thermal performance improvement is explained by complex flow circulation that disrupts the thermal boundary layer growth and dynamic vortex motion that promotes mixing between near-wall fluid and mainstream coolant. Higher pulsation frequency and smaller duty cycle are beneficial for cooling enhancement while the percentage improvement of dimple structure is higher than groove structure, which agrees with the experimental results. Compared to the steady-flow flat heat sink, a maximum enhancement of 45% is obtained by adopting intermittent jet at grooved surface.
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