NUMERICAL INVESTIGATION OF CONFINED SINGLE JET IMPINGING ON A DIMPLED TARGET SURFACE USING Al2O3-WATER NANOFLUIDS

Jet impingement has been investigated widely owing to its high rates of convective heat transfer near the stagnation zone. Nanofluids, beyond the traditional working fluids, have great advantages in high-rate-heat flux removal. In the present work, a confined single jet impinging on a dimpled target surface with Al2O3-water nanofluids as a working fluid was investigated numerically for the first time. The effects of the jet Reynolds number Re-j (10,000-20,000) and nanoparticle volume concentration phi (0-5%) on the fl ow structures and heat transfer characteristics were investigated. The geometrical parameters were H/D-j = 6, D-j/D = 0.5, and delta/D = 0.2. The vorticity contours and streamlines of the confi ned domain, wall shear stress and pressure coeffi cient on the target surface, the pumping power, and the Nusselt number distributions were obtained. The results indicated that the eff ects of Re-j and phi on the fl ow fi eld and heat transfer performance were magnifi ed due to the interaction between them. A fl ow separation emerged near the dimple edge and got smaller with increase in Re-j. The changes of three high vorticity magnitude zones in the confi ned domain depended on the variation of Re-j and phi. The regularity of change in the Nusselt number was complex and the physical properties of the working substance had great eff ect on it. Furthermore, the concept map of the fl ow structures of nanofl uids in confi ned impingement and correlations have been derived from the parameter analysis.