MRT lattice Boltzmann simulation of free convection in a symmetrical annulus combined with experimental data of TiO2-H2O nanofluid's properties

Abstract The axisymmetric nanofluid flow and heat transfer in a two-dimensional vertical annulus are investigated. The Multi-Relaxation-Time lattice Boltzmann model is used to simulate the flow and temperature fields. Hence, the macro cylindrical energy equation is exactly recovered using Chapman-Enskog analysis. The numerical results of the present numerical approach are compared with those existed researches, and it is found that there are close agreements between the results. In addition, the thermo-physical properties of TiO2-H2O nanofluid are measured in the laboratory. The Rayleigh number, nanoparticle concentration of nanofluid and aspect ratio of annulus are governing parameters. It is found that the maximum enhancement of average Nusselt number are about 45% and 94%, respectively; when the volume fraction of nanofluid and Rayleigh number change from their minimum values to maximum values. On the other hand, the maximum increment of total entropy generation is about 57% as the Rayleigh number enhances.