ABSTRACT:
Natural convection heat transfer from extended surfaces is a conspicuous phenomenon in electronic-cooling applications for better thermal management of engineering devices. In this context, the design and thermal performance of wavy annular fins are numerically investigated to elucidate the heat dissipation characteristics from an isothermal horizontal cylinder. The extent and significance of wavy annular fins on the augmentation in momentum and heat transfer characteristics are explicated, considering the impacts of Rayleigh number (Ra), inter-fin-spacing (S/d), fin-diameter (D/d), pitch-to-amplitude ratio (P/A) of the wavy fin, and number of cycles (n) in a wavy-fin. Results are also compared with straight-fin situations to justify the recommendation of wavy-fins over straight-fins. At certain ranges of the pertinent parameters, wavy-fins intensifies the thermo-buoyant flow and augments the heat dissipation from the fin surface. The results reveal that the wavy fins are superior to straight fins at higher Ra and beyond the optimum S/d, whereas straight fins are still better at low Ra and low S/d values. At higher Ra, the average Nusselt number (Nu) and fin-effectiveness are higher for wavy fins of three cycles, followed by two and one cycles beyond the optimum S/d value. Furthermore, the optimum S/d for fin-effectiveness gradually diminishes with increase in Ra and eventually disappears at Ra of 106. This work finds applications in electronic cooling, process cooling chillers, and rice mill heat exchangers. This study affirms to be the very first research work in the realm of annular wavy fins.
