Design of perforated branching fins in laminar natural convection

Under laminar natural convection conditions, the optimum design of a perforated branching fin for electronic cooling application is numerically investigated. Circular perforations with diameters varying between 1.1 mm and 6.6 mm are used. In this size range, the surface area of the perforated fins is less than the non-perforated fins. Two orientations of the fins are considered, namely vertical base horizontal fin (vBhF) and horizontal base vertical fin (hBvF). With a ‘single’ perforated branching fin, heat dissipation is always enhanced by making perforations in vBhF orientation, but it would diminish in hBvF orientation for certain pore sizes and distributions. The optimum values of perforation diameter, pitch and branching angle for heat transfer enhancement are determined to be d = 3.3 mm, PH = 1.05d, PL = 1.5d and α = 45o corresponding to a porosity of 40.5%. High plume velocities and low temperatures observed in 3.3 mm pores made it the optimum size. With a stack of perforated fins, heat dissipation is enhanced for every inter-fin spacing in vBhF orientation, while the enhancement in hBvF orientation is observed only at narrow spacing. Maximum total heat flux dissipated by the stack of perforated fins is 1.6 times higher in hBvF orientation due to significant contribution from convection heat transfer.