Experimental observation and conjugated heat transfer analysis of vortex flow development in mixed convection of air in a horizontal rectangular duct

Abstract

A combined flow visualization and conjugated heat transfer analysis was carried out to study the axial evolution of the buoyancy induced secondary vortex flow in a mixed convective air flow through a bottom heated horizontal rectangular duct. In the experiment the cross plane secondary flow was visualized at selected cross-sections. While in the conjugated analysis, the unsteady three-dimensional Navier-Stokes and energy equations for the flow were coupled with the unsteady two-dimensional conduction equations for the solid walls and were solved together numerically. Results were obtained for the Reynolds number ranging from 35 to 102 and Grashof number from 1600 to 5.8 x 10(5), covering the steady and time periodic flows. Both the experimental and numerical results clearly showed the generation of the longitudinal vortex rolls in the entry half of the duct and the merge of these rolls downstream. At higher buoyancy-to-inertia ratio more rolls were generated and they merged into fewer and larger rolls. Significant conjugated heat transfer effects were noted from the numerical results. Copyright (C) 1996 Elsevier Science Ltd.