Abstract
In this paper, heat transfer and entropy generation of MHD natural convection of Carbone NanoTube (CNT)water nanofluids in a square cavity with and without isothermal block are numerically studied. The cavity is heated sinusoidally, according to the X coordinate, from below and it is cooled isothermally from the top. The two vertical walls are kept adiabatic. Three cases were investigated: square cavity without block (WB), with cold block (CB), and with hot block (HB). The nonlinear governing equations and boundary conditions are discretized using finite volume approach with the Quick scheme and solved numerically by projection algorithm for the pressure-velocity coupling together with the multigrid solver. Simulations were carried out based on various flow-governing parameters such as Hartmann number (0<Ha<45), nanoparticle volume fraction (0<Phi<12%) and for the three considered cases (WB, CB, and HB) with a fixed Rayleigh number Ra= 10(5), Prandtl number Pr=6.2 and irreversibility factor lambda=10(-4). The effects of the pertinent parameters in the performance of the system were investigated. Results show that increasing Ha always ameliorate the system's performance, however, increasing Phi enhances the performance only at high Ha values. Furthermore, the presence of the cold block inside the cavity (CB) was characterized by the greatest values of the Performance Evaluation Criteria (PEC), which means that this case has the best performance compared with the two others cases.