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

• Published in: International journal of thermal sciences 2019-08, Vol.142, p.392-406
• Main Authors: Hoi, Su Min, Teh, An Liang, Ooi, Ean Hin, Chew, Irene Mei Leng, Foo, Ji Jinn
• Format: Article
• Language: English
• Subjects: CFD; Fractal geometry; HVAC; Plate-fin heat sink; Thermal dissipation; Turbulence
• ISSN: 1290-0729; 1778-4166
• DOI: 10.1016/j.ijthermalsci.2019.04.035

The interaction of fractal grid-induced turbulence on plate-fin heat sink is numerically investigated at flow Reynolds number of ReDh = 7.3 × 104. Three fractal grids of different number of fractal iterations N, namely: The rectangular fractal grid of N = 2 (RFG2), square fractal grid of N = 3 (SFG3), and square fractal grid of N = 4 (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 = 7.07 × 103 at δ = 10 and 25 mm, but at a cost of higher ΔP. RFG2's maximum Nu is 6.82 × 103 where wider δ of δ = 50 mm is preferred, and SFG4 is 6.42 × 103 at δ=10 mm. 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. •Fractal insert generated turbulence on plate-fin heat sink forced convection is investigated.•Effects of iteration number N, fractal N = 1 bar thickness t0 and inter-fin distance δ are studied.•Heat dissipation is enhanced by 57%, 51% and 43% via SFG3, RFG2 and SFG4, respectively.•SFG3 incites the most potent inter-fin fluid flow perturbation with U/Uc ≤ 2.175.•Albeit the unique dependency of Nusselt number Nu with N and δ, Nu increases with t0.