Effect of Nozzle Design on Bubbly Jet Entrainment and Oxygen Transfer Efficiency
Publication: Journal of Hydraulic Engineering
Volume 144, Issue 8
Abstract
This study investigates experimentally the effect of nozzle type, including diffusers with single- and multiple-orifices with different diameters, on the hydrodynamics and mass transfer characteristics of air-water bubbly jets discharged at the bottom of a water tank. The results revealed that for the same flow rates of air and water, the total area of the orifices independent of the number of ports controls the initial momentum of the bubbly jets and the jet-to-plume length scale of the flow. An integral model was fitted to the experimental data in order to obtain entrainment coefficients for each test and at different water depths, which confirmed that merged multiple bubbly jets can be analyzed using an equivalent single jet integral model. This resulted in an entrainment relationship described as a function of the kinematic buoyancy flux, bubble slip velocity, and distance from the source, which is similar to that available in the literature for bubble plumes, but with different constants. Finally, the model proposed here is compared to previous models and applied to practical cases including mixing and aeration of tanks and water bodies, indicating that gas transfer efficiency can be significantly enhanced by using multiple-orifice arrangements.
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Acknowledgments
The authors are grateful to the Brazilian National Council for Scientific and Technological Development—CNPq for the Ph.D. scholarship granted to D. D. Lima and for the financial support of this study (Project No. 445211/2014-8). The authors also thank Mr. Ernane Gadelha for building the experimental apparatus.
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Published In
Journal of Hydraulic Engineering
Volume 144 • Issue 8 • August 2018
Copyright
©2018 American Society of Civil Engineers.
History
Received: Jul 14, 2017
Accepted: Feb 22, 2018
Published online: May 30, 2018
Published in print: Aug 1, 2018
Discussion open until: Oct 30, 2018
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