LAUSR

Abstract The flow across the plate-fin heat sink under the influence of 2D planar space-filling square fractal grid-induced turbulence at Reynolds number ReDh of 2.0 × 104 is numerically characterized. Fractal thickness ratio tr, plate-fin inter-fin distance δ and grid-fin separation l are numerically explored and optimized via Response Surface Optimization (RSO) with the objective of maximizing the Nusselt number Nu. Results reveal that, thanks to highly interactive, small and comparable turbulence length scale Lt, strong turbulence intensity Tu and high velocity adjacent to the fin surfaces, thermal dissipation of plate-fin heat sink enhances significantly. An optimum fractal grid and plate-fin geometrical combination having tr = 9.77, δ = 0.005 m and l = 0.01 m is proposed. It delivers Nu of 3661.0 which is 6.1% and 16.3% greater than the reference case and least favorable configuration, respectively. Sensitivity analysis discovered that δ effectively dominates the thermal dissipation improvement while tr contributes the most on the pressure drop. Interestingly, fractal grid may not necessarily augmenting plate-fin forced convective heat transfer. Without proper-tuning the fluid flow structures within the fins may worsen the thermal dissipation instead of strengthening it. In short, the interaction between plate-fin heat sink and the fluid flow structures within the fins contributes greatly to heat transfer performance.