الخلاصة:
In our investigation we have studied and compared the laminar and permanent natural
convection in two-dimensional enclosures (square enclosure, enclosures with curved walls) filled with nanofluid (water-Cu) and subject to three different types of boundary conditions that are: first case (horizontal walls of enclosure are adiabatic, and vertical walls are isothermal maintained at cold temperature Tc and hot temperature Th), second case (vertical walls of enclosures are maintained isothermal at a cold temperature Tc, horizontal top walls are considered adiabatic and bottom walls are maintained isothermal at a constant hot temperature Th), third case (vertical walls of the enclosures are maintained isothermal at a cold temperature Tc, horizontal top walls are considered adiabatic and bottom walls are maintained at a sinusoidal hot temperature). We considered a Newtonian fluid and the flow is
incompressible. The values of Rayleigh number are: 103, 104, 105 and 106, the Prandtl number is fixed to 6.2 and the volume fraction ϕ is taken equal to: 0, 0.1 and 0.2. The method used in this study is the finite volume method. The numerical results obtained show that the heat transfer rate increases both with increasing the volume fraction and the Rayleigh number, and that the average Nusselt number and therefore the heat transfer increases with the increase of the volume fraction of the nanoparticles for the full range of Rayleigh numbers, and that the effect of the nanofluid on natural convection is much more manifest for higher values of Rayleigh number.
