Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.
This paper presents a numerical investigation on airflow
through a heated horizontal rectangular duct wherein the model
considers the combined modes of natural and forced convection
heat transfer and the surface thermal radiation from duct walls.
The duct periphery is differentially heated with known
temperature profiles imposed on the two opposite vertical
sidewalls and the other two walls treated as adiabatic. The air
enters the duct hydrodynamically fully developed and flows
steadily under laminar conditions undergoing thermal
development within the duct. Considering several temperature
profiles on the two vertical sidewalls, the numerical simulation
generates the heat transfer rates and associated fluid flow
patterns in the duct for a range of airflow rates, duct aspect
ratios and surface emissivity. The Nusselt number at duct wall
and the fluid flow patterns are critically examined to identify
thermal instabilities and the significance of wall surface
radiation effects on the overall heat transfer rates.