NATURAL CONVECTION IN A DIAMOND-SHAPED RECEIVING CAVITY HEATED FROM THE BOTTOM CORNER AND FILLED WITH Fe3O4-H2O NANOFLUID IN THE PRESENCE OF THERMAL RADIATION

Abstract

Heat transfer of nanofluid Fe<sub>3</sub>O<sub>4</sub>-H<sub>2</sub>O generated by natural convection and thermal radiation in a diamond-shaped receiving cavity has been investigated numerically. The lower and upper corners of the rhombic receiver are kept isothermal in such a way to provide heating from the lower corner parts and maintain adiabatic the remaining nonactive portions of the walls. The lattice Bolkmann method has been used to simulate fluid flows and highlight the combined effects of the control parameters that are the Rayleigh number (Ra = 10<sup>3</sup> to 2 × 10<sup>6</sup>), the radiation parameter (Rd = 0 to 3), and the nanoparticles' volume fraction (φ = 0 to 4%). The obtained flow structures are either monocellular (MF) or bicellular (BF), depending on the initial conditions and the generated heat transfer rates corresponding to the resulting structures are improved by increasing the Rayleigh number, the nanoparticles' volume fraction, and the radiation parameter. All critical Rayleigh numbers leading to different types of transitions within the considered range of this parameter undergo a change by varying the volume fraction of nanoparticles and the radiation parameter.