Natural convection characteristics of a reacting nanofluid with variable properties in a porous and fluid layered cavity

• Natural convection of a reacting nanofluid in a partitioned cavity is studied. • Effects of magnetic field and variable thermophysical properties are considered. • Flow intensity increases with Rayleigh and Frank-Kamenetskii numbers. • Increasing nanoparticles’ volume fraction leads to increasing and then decreasing tendency. Natural convection in a partitioned enclosure with porous and fluid layers is of research interest due to its occurrence in crude oil production, percolation of chemical pollutants through porous soil, moisture penetration in grain storage, and nuclear waste storage. This study analyzes the natural convection characteristics of a chemically reacting nanofluid in a partitioned cavity considering variable thermophysical properties of the nanofluid and an inclined magnetic field. It is the first investigation to date which considers a chemically reacting nanofluid in a partitioned cavity. Defining suitable variable transformations, the governing equations are reduced to a set of nondimensional equations which are solved numerically using the finite difference method. An increase in Darcy number leads to a decrease in fluid flow of nanofluid layer and an increase in flow velocity of porous layer and maximum temperature. For higher Rayleigh number, the flow intensity and remaining oxidizer concentration increase; however, the maximum temperature diminishes. Moreover, the magnitude of the stream function and maximum temperature increase, while the remaining amount of oxidizer decreases with increasing Frank-Kamenetskii number and Hartmann number. However, the opposite effect is recognized for the increase in the porous layer thickness. As the volume fraction of nanoparticles increases, the maximum temperature first increases and then decreases, while the converse scenario is observed for the magnitude of flow circulation in the fluid layer