Natural convection and thermal radiation analysis inside the square cavity filled with non-Newtonian fluid via heatlines and entropy generation

In the present analysis, natural convection heat transfer coupled with thermal radiation of bi-viscosity fluid contained inside the cavity has been studied through heatlines and entropy generation. Heat is provided to the cavity through heated source with length L/2, which is placed at the middle of bottom wall. Side walls of the enclosure at low temperature i.e. T_c ad rest of the walls are kept an adiabatic. The idea of Bejan heatlines and average Bejan number have been used to visualized the convective heat folw and dominant irreversibility due to fluid flow or heat transfer, respectively. Finite element method with penalty technique has been applied to obtain the solution of governing equations. Results are obtained through numerically and displayed in terms of streamlines, heat flux lines , isotherms, velocity, temperature, entropy, Nusselt number and average Bejan number against the extensive range of bi-viscosity β=0.002-1 and thermal radiation N_R=0-5, at fixed Rayleigh Ra=〖10〗^5 and Prandtl number Pr=10. It is observed that there exist a direct relation between bi-viscosity parameter and convection heat transfer due to buoyancy-driven flow. Moreover, the dominant entropy generation has been reported through heat transfer in the lower region of the cavity with and without thermal radiation.