Experimental investigation into vortex structure and pressure drop across microcavities in 3D integrated electronics

Hydrodynamics in microcavities with cylindrical micropin fin arrays simulating a single layer of a water-cooled electronic chip stack is investigated experimentally. Both inline and staggered pin arrangements are investigated using pressure drop and microparticle image velocimetry (mu PIV) measurements. The pressure drop across the cavity shows a flow transition at pin diameter-based Reynolds numbers (Re (d) ) similar to 200. Instantaneous mu PIV, performed using a pH-controlled high seeding density of tracer microspheres, helps visualize vortex structure unreported till date in microscale geometries. The post-transition flow field shows vortex shedding and flow impingement onto the pins explaining the pressure drop increase. The flow fluctuations start at the chip outlet and shift upstream with increasing Re (d) . No fluctuations are observed for a cavity with pin height-to-diameter ratio h/d = 1 up to Re (d) similar to 330; however, its pressure drop was higher than for a cavity with h/d = 2 due to pronounced influence of cavity walls.