Plate-fin heat sink forced convective heat transfer augmentation with a fractal insert

摘要

The interaction of fractal grid-induced turbulence on plate-fin heat sink is numerically investigated at flow Reynolds number of Re-Dh = 7.3 x 10(4). Three fractal grids of different number of fractal iterations N, namely: The rectangular fractal grid of N = 2 (RFG(2)), square fractal grid of N = 3 (SFG(3)), and square fractal grid of N = 4 (SFG(4)) are employed to perturb the windward fluid flow. For each case, the effects of eight fractal grid first iterative bar thicknesses t(0) at five different inter-fin distances delta are investigated. Results show that Nusselt number Nu and pressure drop Delta P increase with t(0) for all cases. 57%, 51% and 43% of forced convective heat transfer augmentations are observed using SFG(3), RFG(2) and SFG(4), respectively, than that of the control plate-fin heat sink. The thermal and fluid flow perturbation promoted by SFG(3) outperforms the rest with Nu = 7.07 x 10(3) at delta = 10 and 25 mm, but at a cost of higher Delta P. RFG(2)'s maximum Nu is 6.82 x 10(3) where wider delta of delta = 50 mm is preferred, and SFG(4) is 6.42 x 10(3) at delta =10 mm. Interestingly, SFG(4) enjoys a lower Delta P, which is highly energy sustainable. The strength of SFG(3)-induced turbulence intensity is able to infiltrate deeper into the fins at a higher flow rate, which may facilitate the continuous restructuring of inter-fin flow boundary layers, thus promoting thermal dissipation. In short, plate-fin heat sink forced convection is strongly dependent on the interaction between the insert configuration and the induced flow structures within fins, of which, the effects of t(0) and delta are highly correlated.