HEAT TRANSFER ENHANCEMENT CAUSED BY IMPINGING JETS OF Al2O3-WATER NANOFLUID ON AMICRO-PIN FIN ROUGHENED SURFACE UNDER CROSSFLOW CONDITIONS-A NUMERICAL STUDY

Advanced electronic devices need ultrahigh performance cooling techniques. One such technique is jet impingement cooling. This study numerically investigates the thermal performance and flow behavior of an array of alumina oxide-water nanofluid impinging jet systems under crossflow. The Reynolds number of the jet array ranges between 4000 and 20,000 with a normalized distance between the jet's outlet and target plate (Z/D) equal to 3. The target wall is roughened with micro-pin fins for surface enlargement. All of the computations are done in ANSYS-FLUENT using the shear stress transport k-omega turbulence model. The paper reports numerical predictions matching satisfactorily well with the empirical data. However, more research in the context of turbulence models solely for turbulent nanofluid modeling is recommended for future studies. The influence of volumetric concentrations phi = 0%, 0.2%, 0.7%, 1.5%, and 3% of Al2O3 nanoparticles is explored. It is inferred from the simulations that the addition of the nanoparticles does not influence the velocity field with the simplified method used in the current work. It can also be inferred that the increasing values of the nanoparticle concentration would cause a rise in the nanofluid equivalent thermal conductivity leading to a reduction in the Nusselt number, whereas the average convective heat transfer coefficient would improve. About 72% improvement in the heat transfer coefficient (h) of the nanofluid is observed while the Nusselt number is reduced by about 30% at volumetric concentration phi = 3%. The addition of pin fins would help in further heat transfer improvement.