Buoyancy Effects on Laminar Forced Convection in the Thermal Entrance Region of Horizontal Rectangular Channels

Abstract

Buoyancy effects on laminar forced convection in the thermal entrance region of a horizontal square channel for Pr = 0.7, 1, 2, 5, 10, and 100 and Ra = 10{sup 4}, 3 {times} 10{sup 4}, 6 {times} 10{sup 4}, and 10{sup 5} have been studied by Chou and Hwang using a vorticity-velocity method. However, the mixed convection in horizontal rectangular channels with width-to-height aspect ratios other than one is also important in engineering applications. The flow and heat transfer characteristics may be significantly influenced by the aspect ratio. A relatively novel vorticity-velocity formulation of the Navier-Stokes equations and the related numerical scheme were developed by Chou and Hwang to study the laminar mixed convection in the thermal entrance region of a square duct for moderate and small Prandtl number fluids. The purpose of the present investigation is to extend the previous work to channels of aspect ratios {gamma} = 0.2, 0.5, 2, and 5 to examine the effect of aspect ratio on the flow and heat transfer characteristics.