Lattice Boltzmann simulation of nanofluid heat transfer enhancement and entropy generation

In the framework of this paper, nanofluid flow and heat transfer in a square enclosure containing a rectangular heated body is investigated computationally. The fluid in the cavity is a water-based nanofluid containing four different types of metal and metal-oxide nanoparticles: alumina (Al2O3), copper (Cu), silver (Ag) and titania (TiO2). The effective viscosity and thermal conductivity of the nanofluid are calculated by the Brinkman model and Maxwell-Garnett (MG), respectively. The Lattice Boltzmann Method (LBM) has been adopted to solve this problem. The effects of various governing parameters such as nanofluid type, Rayleigh number, volume fraction of nanoparticles and height of the rectangular heated body contained in the cavity on hydrothermal characteristics are studied. The results indicate that both the Nusselt number and dimensionless entropy generation are increasing functions of the Rayleigh number and nanoparticle volume fraction of the nanofluid. Furthermore, the effect of nanoparticle volume fraction is found to be more pronounced for a low Rayleigh number as compared to a high Rayleigh number. Excellent accuracy is achieved with the LBM code.