Significance of variable fluid properties on hybrid nanoliquid flow in a micro-annulus with quadratic convection and quadratic thermal radiation: Response surface methodology

Many engineering and manufacturing processes such as heat storage systems, nuclear power plants, and heat exchangers operate at high temperatures. The temperature gradient in these systems is significantly large so that the transport properties of the fluid are significantly influenced. In such cases considering the constant thermophysical properties for ambient liquid and adopting linear Boussinesq approximation become insignificant. Therefore, in this study, the quadratic convective flow of water-based Ag-MgO hybrid nanoliquid in a micro-annulus with variable viscosity and thermal conductivity is investigated under the temperature jump and velocity slip auxiliary conditions. The effects of quadratic Boussinesq approximation and quadratic Rosseland radiative heat are also addressed. The correlation for effective viscosity and thermal conductivity are modeled by employing the experimental work of Esfe and his collaborators (so-called Esfe Model). The nonlinear dimensionless governing equations are solved numerically using the finite difference method. Further, the sensitivity analysis using response surface methodology (RSM) is performed to enhance the understanding of heat transport behavior. The significance of various flow parameters involving in the current problem is analyzed through 2D and 3D-surface plots. This study portrays that the consequence of quadratic convection, velocity slip, and variable viscosity aspects are positively related to the growth of the momentum layer structure. The heat transport rate is found to be more dominated by quadratic radiation compared to the addition of nanoparticles and temperature variation aspect. The variable viscosity, quadratic convection, and quadratic thermal radiation mechanisms lead to higher skin friction. The thermal layer structure augments with the temperature variation aspect. Furthermore, the sensitivity of the Nusselt number to the addition of nanoparticles and quadratic radiation is always positive.