Numerical Simulation of Natural Convection of Water Based Nanofluids in Horizontal Eccentric Cylindrical Annuli

The natural convection fluid flow and heat transfer in an annuli of two differentially heated eccentric cylindrical duct filled with the Cu-water nanofluid are investigated numerically. The outer cylinder is maintained at a constant temperature T-c while the inner cylinder is kept at a differentially higher constant temperature T-h. The flow is assumed to be incompressible and laminar. The governing equations are written in the bicylindrical coordinates system and solved via finite volume method. Calculations were performed for Rayleigh number (10(3) <= Ra <= 10(6)), volume fraction of nanoparticles (0 <= phi <= 0.1). The eccentricity and radii ratio are fixed at 0.4 and 0.5, respectively. Results are presented in the form of stream lines, isotherm plots, local and average Nusselt numbers. The numerical results obtained indicate that, for high values of Rayleigh number, an enhancement in heat transfer is achieved around the inner cylinder surface due to the presence of Cu nanoparticles except in the plume region. Moreover, it is observed from the results that, the average Nusselt number and stream functions increase by increasing the volume fraction of the nanoparticles.