Three-Dimensional Computational Fluid Dynamics Analysis of Convective Heat Transfer From a Heated Horizontal Cylinder Rotating in Air: From Laminar to Turbulent Flow

Abstract A 3D computational fluid dynamics model is developed to reproduce the results of previous experiments and to investigate the correlation between Nusselt numbers and convection heat transfer phenomena surrounding an isothermal rotating cylinder. The simulation is conducted in a quiescent air domain and a fixed Grashof number of 2.32 × 108 for a horizontal cylinder placed in air with rotational speeds ranging from 2.43 to 103.22 RPM. The effects of buoyancy-induced flows and the rotational Reynolds number Rer on convective heat transfer characteristics are investigated. At low Rer, buoyancy-driven Rayleigh–Bénard convection dominates, forming vertically extended thermal plumes obstructing heat convection on the upper side of the cylinder, leading to lower Nusselt number in these regions. As Rer increases, rotational effects intensify, flow plumes merge with the cylinder surface and thicken the thermal boundary layers, on the other hand enhancing turbulent mixing, thus ultimately improving heat transfer. The circumferential Nusselt number distribution further highlights that plume formation lowers Nusselt numbers on the descending side, while heat transfer is enhanced along the axial direction toward the cylinder ends, where the thermal boundary layer thickness gradually decreases.