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,

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 (KLa) 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 KLa as the total bubble surface area increases. The rate of increase of KLa, 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: Turbulent flow | Shear flow | Oxygen transfer | Air flow | Fluid velocity | Aeration | Water discharge | Turbulence

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