Evaluation of Al₂O₃-Water nanofluid in a microchannel equipped with a synthetic jet using single-phase and Eulerian–Lagrangian models

The present work is focused on a novel cooling device consisting of a microchannel and nanofluid synthetic jet generated through the activation of membrane oscillation at frequencies (f) of 280, 420 and 560 Hz and five different amplitudes (A) ranging from 20 to 40 μm Al₂O₃ nanoparticles in the fluid domain are set at particle volume fractions (φ) of 2, 3 and 5% with diameter sizes of 50, 75 and 100 nm. The single-phase model (SPM) and Eulerian-Lagrangian (DPM) model are applied and compared to examine the fluid flow and heat transfer enhancement followed by validation against experimental data. Parametric studies reveal that the best heat transfer enhancement is found at a setting of φ = 2% and an oscillating frequency of 560 Hz with an amplitude of 30 μm for nanoparticles 100 nm in size. Comparison between SPM and DPM shows that there is an over-prediction of heat transfer enhancement in the SPM while DPM cooling is more realistic through the consideration of different forces acting on the particles and base fluid. The thermophoresis force is identified as the most significant force contributing to the heat transfer coefficient. It is further concluded that better heat transfer enhancement is achieved through the adoption of smaller particle diameters and higher oscillation membrane frequencies.