Two- and three-dimensional comparative study of heat transfer and pressure drop characteristics of nanofluids flow through a ventilated cubic cavity (part II: non-Newtonian nanofluids under the influence of a magnetic field)

Abstract

In this paper, we study numerically the incompressible laminar mixed convection flow of Zinc Oxide nanolubricants in ventilated cavities (2D and 3D cavities), under the influence of a uniform magnetic field at various inclination angles. The ventilation is assured by two openings of the same size, located at the vertical walls, where the cold nanofluid enters through the opening, located at the top of the left wall, and exits through the second, located at the bottom of the right wall. All walls are considered hot except the lateral walls of the 3D configuration which are adiabatic. The non-Newtonian nanofluid (nanolubricants) considered in this study obeys the rheological model of Bingham. Incorporating the exponential Papanastasiou regularization approach of this model, the governing equations of the physical problem are discretized, using the finite volume method and the SIMPLER algorithm for the pressure–velocity coupling. For a wide range of pertinent control parameters, namely the Reynolds number and the nanoparticles volume fraction as well as the inclination angle of the magnetic field, at a fixed Hartmann number Ha = 100, the results show that, with/without magnetic field, the average Nusselt number increases and the pressure drop decreases with the Reynolds number. The presence of the magnetic field meaningfully increases the heat exchange and increases dramatically the pressure drop, compared to the case without a magnetic field, except for an inclination angle ω = 135°, where the heat exchange rate is reduced. However, nanoparticles improve heat exchange only beyond a yield value of the nanoparticles volume fraction and then become disadvantageous. In addition, the extent of the rigid zone is amplified with the nanoparticles volume fraction and the magnetic field. Finally, the optimal angle offering the best performance is ω = 0°. In addition, the introduction of nanoparticles and the increase in the inertial force increase the gap between the two configurations (2D and 3D). On the other hand, Lorentz’s force weakens the effect of the third direction.