Oxygen Transfer in Turbulent Shear Flows

by Kyung Soo Jun, Univ of Iowa, Iowa City, United States,
Subhash C. Jain, Univ of Iowa, Iowa City, United States,



Document Type: Proceeding Paper

Part of: Water Quality Issues at Fossil Fuel Plants

Abstract:

Oxygen transfer equation for the air-water two-phase aeration region of turbulent shear flow in a vertical pipe is derived. Dimensionless variables significant in characterizing the transfer coefficient in turbulent shear flow are identified from considerations of turbulent intensity and eddy scales. Laboratory experiments are conducted for various flow velocities and air flow rates. The overall transfer coefficient (K_La) and bubble size distribution are measured to compute the transfer coefficient (k). For a given air-water discharge ratio, higher flow velocity of water gives a larger k due to higher turbulence intensity. As the air-water ratio increases at a given flow velocity, so does K_La as the total bubble surface area increases. The rate of increase of K_La, however, becomes smaller since k decreases for larger air-water discharge ratios. The reduction of k results from the decrease of turbulence intensity per unit volume of air.

Subject Headings: Shear flow | Turbulent flow | Oxygen transfer | Turbulence | Fluid velocity | Fluid flow | Air flow

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