This article presents a numerical study on natural convection heat transfer of nanofluid (Cu-water) in a square enclosure having a cold obstacle. The transport equations were solved using the finite difference formulation based on Alternating Direction Implicit method (ADI method). The method used is validated against previous works. Effects of various design parameters such as the height of the obstacle (0.125≤H≤0.5), Rayleigh number (〖10〗^3 ≤ Ra ≤ 〖10〗^6), and nanoparticles volume fraction (0 ≤ φ ≤ 0.2) on the heat transfer are investigated. The results show that the heat transfer rate inside the enclosure increases by increasing the height of the cold block, the volume fraction of nanoparticles and Rayleigh number.
The aim of this paper, is to use a more realistic model which incorporates the effects of Brownian motion and the thermophoresis for studying the effect of some control parameters on the onset of convective instability in a rotating medium filled of a Newtonian nanofluid layer and heated from below, this layer is assumed to have a low concentration of nanoparticles. The linear study which was achieved in this investigation shows that the thermal stability of Newtonian nanofluids depends of the buoyancy forces, the Coriolis force generated by the rotation of the system, the Brownian motion, the thermophoresis and other thermo-physical properties of nanoparticles. The studied problem will be solved analytically by converting our boundary value problem to an initial value problem, after this step we will approach numerically the searched solutions by polynomials of high degree to obtain a fifth-order-accurate solution.
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