Heat Transfer Augmentation Using Scale-Roughened Surfaces for Low-Reynolds Number Flows Generated by Piezoelectric Fans

We report a study of heat transfer augmentation enabled by structured surfaces at relatively low Reynolds numbers (120 <; Re <; 2750), with potential applications in electronics cooling. The experiments are done in two phases to cover the full Reynolds range. In the first phase, surfaces containing fish scale-like patterns are tested in a rectangular channel with Reynolds numbers in the range of 1000 <; Re
_c
<; 2750 to investigate the effects of the pattern height and flow direction on the Nusselt number and the pressure drop. We observe up to 60% improvement in the Nusselt number of the scale-roughened surfaces for the tallest (1 mm) patterns tested and no commensurate increase in the pressure drop when compared with the featureless flat surface. In the second phase, we examine enhancement in the convective cooling of scale-roughened surfaces using piezoelectric fans aligned perpendicular to the surfaces in the range of 120 <; Re
_p
<; 1000. For jet-like flows generated by piezoelectric fans, the Nusselt number is increased by approximately 14%. Our results show that scale-patterned surfaces are promising to enable power-efficient thermal management solutions even at low Reynolds numbers.