Experimental investigation of laminar flow across short micro pin fin arrays

The pressure drop and friction factor of gas flow across an array of circular silicon micro-pillars with different diameters fabricated by deep reactive ion etch (DRIE) process were investigated. The pitch-to-diameter ratio (1.5 < S-T/d < 2.3) and the height-to-diameter aspect ratio (0.48 < H/d < 2.28) were found to affect the friction factor of the pillar array significantly. A new correlation, which considered the coupled effect of pillar spacing and aspect ratio, was proposed to predict the friction factor in a Reynolds number range of 1-100. Silicon pillars with large artificial roughness amplitudes were also fabricated, and the effect of the roughness was studied in the laminar flow region. The results demonstrated that the pressure drop and the friction factor were reduced significantly (more than 50%) for the pillar array with a large artificial roughness, which may be used to improve the cooling efficiency for the regenerator structures in micro-coolers.