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

摘要

This dissertation presents a numerical simulation of three-dimensional flow andheat 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 radiativelyparticipating. Governing momentum equations, energy equation, and the radiativeequation were solved by a finite volume method. Extensive validation studies werecarried out. As part of the validation study, three-dimensional combined convection andradiation in a rectangular channel without a backward-facing step was studied. TheSIMPLE algorithm was used to link pressure and velocity fields. The combinedconvective-radiative heat transfer were studied by varying three parameters, i.e. opticalthickness ( H ? =0.1, 0.2, and 0.4) and scattering albedo ( ?=0, 0.25, 0.5, 0.75 and 1).Variation of thermophysical properties with temperature was considered in this study. Inthis work consideration was given only to cooling. Effects of those radiative parameterson velocity, bulk temperature, and Nusselt number are presented in detail. The fluid witha 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 adecrease in optical thickness and an increase in scattering albedo. Thermal penetrationincreased with increasing optical thickness and decreasing scattering albedo. Thereattachment length varied with temperature due to variation of thermophysicalproperties with temperature.