SUMMARY

Forced convection heat transfer in compact heat sinks of high-power air side heat exchangers that are characterized by dense, high aspect ratio
fin channels is typically governed by the inherently low channel Reynolds number (Re) designed to minimize flow losses and cooling power.
However, this low Reynolds number limits the local heat transfer from the fin surface within the thin thermal boundary layers, and the heat
transport by the core flow that relies on mixing with the surface-heated air. These limitations are commonly overcome by increased air volume
flow rate or fin density (increasing the channel Re or the heat transfer area, respectively) that lead to significant rise in flow losses and cooling
power, and increased weight and volume. The two closely-coupled stages of heat transport within the fin channels can be enhanced by
unsteady flow fluctuations and mixing as the flow rate increases or, alternatively, by deliberate introduction of secondary vortices using surfacemounted
vortex generators (albeit at increased losses). The proposed investigations are built on earlier work at Georgia Tech that demonstrated
improved thermal performance for given heat flux and surface temperature but at reduced air flow rate and pressure losses. The proposed PhD
dissertation will focus on identifying the fundamental flow mechanisms associated with the formation and advection of reed-engendered smallscale
motions that lead to heat transfer enhancement within a mm-scale model of the rectangular heat sink channels. Flow diagnostics will
include high-resolution particle image velocimetry (PIV), high-speed imaging of the reed motion, measurements of temperature distributions and
pressure. Of particular interest are the increases in heat dissipation and the associated fluid power over a range of flow rates and reed lengths.