Mixed convection heat transfer in the entrance region of horizontal annuli

The present study deals with a numerical investigation of steady laminar mi xed convection heat transfer in a horizontal concentric annulus using air a nd water as the working fluid. Special attention has been paid to the entra nce region effect. The thermal boundary condition chosen is that of uniform heat flux at the inner wall and an adiabatic outer wall. The basic numeric al procedure used is the SIMPLE algorithm [Int. J. Heat Mass Transfer 15 (2 972) 1787] which uses the finite difference method for solving the momentum and energy equations. The investigations reveal that the Nusselt numbers f or air are considerably greater than the corresponding values for fully dev eloped mixed convection values over a significant portion of the annular du ct. The numerical results were supplemented with some experimentally obtain ed data. (C) 2001 Elsevier Science Ltd. All rights reserved.