Natural convection of nanofluid-filled annulus with cooled and heated sources and rotating cylinder in the water near the density inversion point

Convection heat transfer in an annulus with pair sources and the inner rotating circular cylinder is studied numerically. Cu-water nanofluid is used to fill between the cylinders. Two pair sources (T-c and T-h) were placed around outer and inner cylinders, and others were considered adiabatic. The governing equations were solved on a non-uniform computational mesh in the rotating circular cylinder. They were formulated by considering Boussinesq approximation and water near the density inversion point using the finite volume method. The effects of non-dimensional angular rotational velocity (- 700 <= Omega <= 700), volume fractions of nanoparticles (0.0 <= phi <= 0.08), different locations of sources, thermal conductivity and dynamic viscosity were investigated. The Rayleigh number and the Prandtl number were fixed at Ra = 10(5) and Pr = 13.31. The present work was validated by previous experimental (Kuehn and Goldstein, J Fluid Mech 7 4:695-719, 1976) and numerical studies (Abu-Nada et al., Int Commun Heat Mass Trans 35:657-665, 2008; Roslan et al. Int J Heat Mass Trans 55:7247-7256, 2012). The results were presented as the average Nusselt number, thermal conductivity, and dynamic viscosity. They also showed the rotating cylinder, adding nanoparticles, and considering Boussinesq approximation and water near the density inversion point affected improving the heat transfer's rate. The non-dimensional angular rotational velocity and nanofluid increased the heat transfer rate. Also, results indicated which angular rotational velocity and volume fraction of nanoparticles were useful for the industry and specialize in the reactor.

Automated summary

Numerical study was conducted on convection heat transfer in an annulus filled with Cu-water nanofluid between two cylinders. The results showed that the rotating cylinder, addition of nanoparticles, and consideration of Boussinesq approximation and water near the density inversion point improved the heat transfer rate.