MHD NATURAL CONVECTION IN VERTICAL ANNULUS] {MHD NATURAL CONVECTION WITH RADIAL HEAT AND MASS TRANSFER UNDER HEAT AND MASS ABSORPTION IN A VERTICAL ANNULUS

Abstract

This study presents an analytical investigation of the combined effects of an applied radial magnetic field, an induced magnetic field, and inverse-square heat and mass absorption on fully developed natural convection flow of laminar, viscous incompressible electrically conducting fluid. The governing equations are formulated non-dimensionally and solved analytically under steady-state conditions. Key dimensionless parameters, such as the Hartmann number (Ha), heat absorption parameter (S), chemical reaction parameter ($K^*$) and annular gap ratio ($\lambda$), are systematically varied to examine their effects on velocity, temperature, concentration, magnetic field, and induced current density distributions. The results indicate that increasing Hartmann number suppresses velocity due to Lorentz force effects while enhancing the magnetic field intensity. The annular gap $\lambda$ significantly influences flow dynamics, enhancing heat and mass transfer. Higher heat absorption decreases velocity and temperature, confirming its role in energy extraction, while an increase in ($K^*$) depletes concentration as a result of accelerated species diffusion. Furthermore, isothermal boundary conditions exhibit higher distributions profiles compared to iso-flux conditions, demonstrating improved convective transport. The numerical results indicate that increasing Ha generally decreases skin friction, attributed to the Lorentz force. Under isothermal conditions, higher Ha leads to a decline in $\tau_\lambda$ and Q, while for the iso-flux case, $J_\theta$ shows irregular variations, including negative values suggesting a current reversal. Increasing the annular gap ($\lambda$) raises skin friction. Nusselt number (Nu), decreases with increasing $\lambda$, but increases with higher S, indicating that heat absorption promotes efficient convective transport. Isothermal conditions show more effective heat transfer than iso-flux conditions. The ratio of the mass transfer coefficient (Sh) goes down as $\lambda$ goes up and goes up as ($K^*$) goes up. The iso-flux condition consistently produces lower Sherwood numbers, which means that mass transfer is less effective. These findings offer essential insights for enhancing MHD-driven thermal and mass transport systems, applicable in electromagnetic propulsion, nuclear reactor cooling, and advanced energy conversion technologies.