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

Abstract

Abstract The interaction of fractal grid-induced turbulence on plate-fin heat sink is numerically investigated at flow Reynolds number of ReDh\u202f=\u202f7.3\u202f×\u202f104. Three fractal grids of different number of fractal iterations N, namely: The rectangular fractal grid of N\u202f=\u202f2 (RFG2), square fractal grid of N\u202f=\u202f3 (SFG3), and square fractal grid of N\u202f=\u202f4 (SFG4) are employed to perturb the windward fluid flow. For each case, the effects of eight fractal grid first iterative bar thicknesses t0 at five different inter-fin distances δ are investigated. Results show that Nusselt number Nu and pressure drop ΔP increase with t0 for all cases. 57%, 51% and 43% of forced convective heat transfer augmentations are observed using SFG3, RFG2 and SFG4, respectively, than that of the control plate-fin heat sink. The thermal and fluid flow perturbation promoted by SFG3 outperforms the rest with Nu\u202f=\u202f7.07\u202f×\u202f103\u202fat δ\u202f=\u202f10 and 25\u202fmm, but at a cost of higher ΔP. RFG2 s maximum Nu is 6.82\u202f×\u202f103 where wider δ of δ\u202f=\u202f50\u202fmm is preferred, and SFG4 is 6.42\u202f×\u202f103\u202fat δ=10\u202fmm. Interestingly, SFG4 enjoys a lower ΔP, which is highly energy sustainable. The strength of SFG3-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 t0 and δ are highly correlated.