This paper addresses an investigation of flue gas injection on natural draft cooling tower performance through numerical simulation. The control volume finite difference method was used for discretizing the governing equations in axisymmetric form on a boundary-fitted grid. The five independent variables addressed in this study are flue gas flow rate, flue gas temperature, radial injection location, injection orientation, and liquid entrainment in the flue gas. The flue gas temperature was found to have the most significant effect on tower performance (cold water temperature), because it strongly affects the buoyancy within the tower. The total air flow through a tower is driven by buoyancy forces, and the cooling performance is a strong function of the airflow rate.

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A numerical model has been developed to predict the behavior of a buoyant round jet discharging into a quiescent, but thermally stratified ambient. The model has numerous applications for studying jet or plume dilution characteristics. The model has been applied for optimizing surface water pump operation for improving dissolved oxygen (DO) content in hydropower plant releases, without disturbing reservoir bottom sediment. The model predicts velocity, density, and concentration of a conserved species within the jet, and jet radius as a function of the distance from the initial point of discharge. The model relies on an empirically based function for computing the rate of jet entrainment. Predictions of mean velocity from the one dimensional model were compared to field velocity measurements taken in the jet below a surface water pump with excellent agreement. In addition the predicted penetration depth of the jet was in good agreement with field data.

Tom Eldredge received his B.S., M.S., and Ph.D. degrees all in mechanical engineering from the University of Tennessee. He is an Associate Professor of mechanical engineering at Liberty University. He is a Professional Engineer, licensed in the state of Connecticut. Tom Eldredge has over 25 years of experience in computational fluid dynamics (CFD) modeling, related to the power industry for design of combustion systems, cooling tower modeling, and hydro power applications. He has an interest in energy research, particularly as it relates to the thermal sciences and fluid mechanics.

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