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

Skanthan, S., Yeoh, C.V., Chin, W.M., and Foo, J.J., International Journal of Thermal Sciences 125, 176-184, 2018

The continual miniaturization of electronic components has led to increasing levels of thermal dissipation rateper unit volume. The present 3D numerical study proposes a novel method to enhance thermal dissipation viaforced convective heat transfer with a 2D planar space-filling insert. Effects of grid curvature were investigatedby comparing a circular fractal grid (CFG) to a square fractal grid (SFG) and a control regular grid (RG) ofapproximately equivalent blockage ratio. The fractal configurations employed possess similar thickness ratios toensure 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 andthermal dissipation were solved numerically with the Reynolds Stress Model (RSM) and standard energyequation. Results show that the sharp curvature discontinuities and higher exposed surface area in the SFG leadsto a higher Nusselt number. While the SFG has, a higher pressure drop, ΔP, as compared to CFG and RG, theenhancement in forced convective heat transfer offsets the higher ΔP, which results in a higher overall systemperformance. 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 thanthat of SFG and RG. This suggests the pivotal role of curvature in enhancing the mixing properties of a spacefillinginsert.

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