Using a vectorized finite-difference marching technique, the steady-state continuity, momentum, and energy equations are solved numerically to evaluate the effects of buoyancy-induced secondary flow on forced flow in a horizontal rectangular duct with uniform bottom heating. Combined entry region conditions are considered, and the secondary flow is found to consist of longitudinal plumes and vortices that first develop at the vertical sidewalls and subsequently propagate to interior spanwise positions. Sequential stages of the secondary flow development are computed in detail and used to interpret the nonmonotonic longitudinal distribution of the spanwise average Nusselt number. The distribution is characterized by oscillations that, under certain conditions, are damped and yield a fully developed Nusselt number that substantially exceeds the value for pure forced convection.

Development of laminar mixed convection flow in a horizontal rectangular duct with uniform bottom heating

Structures of laminar wakes and heat transfer in the presence of thermal buoyancy art investigated from the numerical solution of complete Navier-Stokes and energy equations in a two-dimensional horizontal channel with a built-in square cylinder. Results show that mixed convection can initiate periodicity and asymmetry in the wake at lower Reynolds numbers than forced convection alone. For a given Reynolds number, the heating of the fluid in the channel is improved by mixed convection up to a certain Grashof number and deteriorates if the Grashof number is further increased.

Numerical investigation of mixed convection heat transfer in a horizontal channel with a built-in square cylinder

Mixed convection with flow reversal in the thermal entrance region of horizontal and vertical pipes

Combined heat and mass transfer for laminar flow of moist air in a 3D rectangular duct: CFD simulation and validation with experimental data

Mixed convection heat transfer in horizontal rectangular ducts with radiation effects

Numerical solutions are given without the aid of a large Prandtl number assumption for combined forced and free laminar convection in the entrance region of a horizontal pipe with uniform wall temperature. The steady-state solutions have been obtained from the asymptotic time solutions of the time-dependent equations of momentum and energy with the Poisson equation for pressure. Results are presented for the developing primary and secondary velocity profiles, developing temperature fields, local wall shear stress, and local and average Nusselt numbers, which reveal how the developing flow and heat transfer in the entrance region are affected by the secondary flow due to buoyancy forces.

M. S. Montesclaros

Papers

Combined Forced and Free Convection in the Entrance Region of an Isothermally Heated Horizontal Pipe