An experimental study on heat transfer and fluid flow of a synthetic jet impinging on a surface roughened with pin fins

Abstract

This study presents a first time comprehensive experimental investigation on the thermo-fluidic interaction between a synthetic jet (SJ) and a pin-fin roughened target surface, emphasizing the effect of fin geometry, radial placement, and arrangement on heat transfer enhancement. Four fin configurations (60°, 72°, 90°, and 120°) were examined at three radial locations and different orifice-to-surface spacings. The results reveal that introducing fins dramatically alters the wall jet structure by generating secondary wall jets, suppressing recirculation near the stagnation region, and increasing turbulence intensity. These effects lead to substantial heat transfer augmentation compared to a smooth surface. Among all tested configurations, the 60° and 72° fin arrangements demonstrated superior thermal performance, achieving nearly identical results with up to 87.6% enhancement in heat transfer at r/d = 1 and z/d = 1. Fins positioned beyond r/d = 2 contributed negligibly to thermal improvement. The two-row configuration was identified as the most efficient design, delivering comparable heat transfer to the three-row arrangement while minimizing material use and flow obstruction. Furthermore, the inline fin arrangement enhanced heat transfer by up to 22.6% compared to the staggered layout due to improved momentum retention and stronger secondary wall jet formation. Flow visualization using the smoke-wire technique confirmed the suppression of large recirculation zones and the emergence of coherent secondary jets that strengthen near-wall convection. Overall, the results establish that optimizing fin geometry and placement, particularly the two-row, 72° inline configuration, can significantly elevate the cooling efficiency of synthetic jet systems, offering a compact, energy-efficient solution for high-heat-flux electronic and aerospace applications. Copyright © 2024. Published by Elsevier Ltd.