Natural convection of nanofluid-filled annulus with cooled and heated sources and rotating cylinder in the water near the density inversion point
Department of Mechanical Engineering, Center of Computational Energy, Hakim Sabzevari University, Sabzevar, Iran
Accepted: 15 May 2021
Published online: 13 August 2021
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 (Tc and Th) 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 ≤ Ω ≤ 700), volume fractions of nanoparticles (0.0 ≤ ϕ ≤ 0.08), different locations of sources, thermal conductivity and dynamic viscosity were investigated. The Rayleigh number and the Prandtl number were fixed at Ra = 105 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.
© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2021