The present paper covers the comparison of two different configurations (square and circular) pinfin heat sinks embedded with two different phase change materials (PCMs) namely paraffin wax and n-eicosane having different thermo-physical properties were carried out for passive cooling of electronic devices. The pin-fins, acting as thermal conductivity enhancers (TCEs), of 2 square and 3 circular fin thickness of constant volume fraction of 9% are chosen and input heat fluxes from 1.2 / 2 to 3.2 / 2 with an increment of 0.4 / 2 are provided. Two different critical set point temperatures (SPTs) 45℃ and 65℃ are chosen to explore the thermal performance in terms of enhancement ratios, enhancement in operation time, latent heating phase duration, thermal capacity and conductance. The results show that 3 diameter of circular pinfins has the best thermal performance in passive thermal management of electronic devices.

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The hydrodynamic behavior of a turbulent flow and the mixing characteristics generated by a V-grooved axial impeller inside an agitated tank reactor were investigated both experimentally and numerically. Angle resolved Particle Image Velocimetry (PIV) techniques with an angular displacement Δθ=5° have been applied and two aerodynamic planes along the blades were considered. PIV-based results were compared to those obtained by Large Eddy Simulation (LES), used with the dynamic Smagorinsky-Lilly sub-grid scale (SGS) model. Results showed the existence of distinctive recirculation zones in the aerodynamic planes, and new additional frequencies in the impeller stream, induced by the grooves. A decrease of mixing time of about 11 % was obtained experimentally, consequence of the better suction induced by the grooved blades in the early stages of mixing. Mean velocities, vorticity, TKE obtained from LES showed a good agreement with the PIV-based results. The distributions of turbulence dissipation rate ε were similar to those obtained from PIV, however showing high under-predicted magnitudes.