Numerical Simulation of Three-Dimensional Combined Convective Radiative Heat Transfer in Rectangular Channels

This dissertation presents a numerical simulation of three-dimensional flow and heat transfer in a channel with a backward-facing step. Flow was considered to be steady, incompressible, and laminar. The flow medium was treated to be radiatively participating. Governing momentum equations, energy equation, and the radiative equation were solved by a finite volume method. Extensive validation studies were carried out. As part of the validation study, three-dimensional combined convection and radiation in a rectangular channel without a backward-facing step was studied. The SIMPLE algorithm was used to link pressure and velocity fields. The combined convective-radiative heat transfer were studied by varying three parameters, i.e. optical thickness ( H τ =0.1, 0.2, and 0.4) and scattering albedo ( ω=0, 0.25, 0.5, 0.75 and 1). Variation of thermophysical properties with temperature was considered in this study. In this work consideration was given only to cooling. Effects of those radiative parameters on velocity, bulk temperature, and Nusselt number are presented in detail. The fluid with a hot inlet compared to a cold wall was cooled in a relatively short distance from the channel inlet because of the radiation effect. The thermal penetration decreased with a decrease in optical thickness and an increase in scattering albedo. Thermal penetration increased with increasing optical thickness and decreasing scattering albedo. The reattachment length varied with temperature due to variation of thermophysical properties with temperature