Effect of Centrifugal Buoyancy on Turbuleut Heat Transfer in an Orthogonally Rotating Square Duct with Transverse or Angled Rib Turbulators

Abstract

Heat transfer in a rotating square rib-roughened duct was numerically simulated in coordinates fitted to angled ribs. In order to investigate the effect of the Coriolis and buoyancy forces on the turbulent heat transfer disturbed by transverse or angled rib turbulators, the large eddy simulation was adopted with a Lagrangian dynamic subgrid-scale model. For a turbulent Reynolds number of 350, rotating conditions of which the rotation number was 1.0 were computed for rib angles of 90 deg and 60 deg. The Rayleigh number was varied from -5×10⁴ to +5×10⁴;the positive and negative values of the Rayleigh number corresponded to radially outward and inward flows, respectively. The present results clearly showed that the heat transfer was enhanced and suppressed by the aiding and opposing flows induced by the buoyancy, respectively. The friction factor of 60 deg rib was decreased for the increase of the Rayleigh number;on the contrary, the 90 deg rib case gave the increased values.