Forced convective heat transfer and flow characteristics of fractal grid heat sinks

Abstract

The continual miniaturization of electronic components has led to increasing levels of thermal dissipation rate per unit volume. The present 3D numerical study proposes a novel method to enhance thermal dissipation via forced convective heat transfer with a 2D planar space-filling insert. Effects of grid curvature were investigated by comparing a circular fractal grid (CFG) to a square fractal grid (SFG) and a control regular grid (RG) of approximately equivalent blockage ratio. The fractal configurations employed possess similar thickness ratios to ensure an integrated comparison based on the interstitial curvatures of CFG and SFG. Heat flux of 20 × 103 W/m2 was applied along the four sides of each insert at Reynolds number of Reh = 2.04 × 104. The flow field and thermal dissipation were solved numerically with the Reynolds Stress Model (RSM) and standard energy equation. Results show that the sharp curvature discontinuities and higher exposed surface area in the SFG leads to a higher Nusselt number. While the SFG has, a higher pressure drop, ΔP, as compared to CFG and RG, the enhancement in forced convective heat transfer offsets the higher ΔP, which results in a higher overall system performance. By this measure of performance, the SFG and CFG outperforms the RG by 35% and 9%, respectively. In terms of turbulent mixing, the CFG achieves higher turbulent intensities leeward from the grid than that of SFG and RG. This suggests the pivotal role of curvature in enhancing the mixing properties of a space-filling insert.