Effect of thermal radiation on MHD mixed convection in an encloser with semicircular heater using kerosene based CNT nanofluid

Abstract

Oil-based nanofluids are used to strengthen the stability of nanofluids as well as their thermophysical properties when they are exposed to high temperature.For this study,heat transfer enhancement on time dependent combined convective flow were examined numerically. A lid-driven square cavity with a semicircular heater on the bottom wall is selected as fluid domain with kerosene-based CNT nanofluid, that is considered for an unsteady, laminar,newtonian, incompressible,and mixed convection flow in the existence of radiative heat flux and magnetic field.The upper wall slides to the x-direction with an isothermal temperature value ofTc and constant velocity u0, whilst the semi-circular heater stays at isothermal temperature Th with a radius of 0.25L and Th>Tc.The other walls of the fluid domain are considered insulated, so there is no heat transfer took place in those regions. The governing two-dimensional equations and associated boundary conditions were presented mathematically for the considered physical problem. The governing equations and boundary conditions are transformed into non-dimensional form and solved using a finite-element approach based on Galerkin weighted residuals.The thermal conductivity and dynamic viscosity models incorporated nanoparticle Brownian motion.The simulations were carried out with a range of values for the radiation parameter Rd (= 0 – 2), the Hartmann number Ha (= 0 – 50), the solid volume fraction ϕ (= 0% – 10%), the Reynolds number Re (= 50 – 200), and the Richardson number Ri (= 0.1-10).Numerous features such as streamlines, isotherms,heat transfer rate of the semicircular heater Nuhand thermophysical properties such as Drag force of the moving lid, fluid temperature gradient θf, fluid pressure gradient Grad P, average fluid temperature θav, fluid bulk temperature θbvelocity magnitude of the fluid were describedfor dimensionless timeτ (= 0 – 1) and the aforesaid parameters.The results show that the indicated parameters have a strong influence on the flow phenomena and temperature field inside the cavity,but have a negligible effect for higher value of dimensionless time. It is worth noted that after a while, the considered parameter exhibits consistent behavior.