The Effect of Nozzle Type on Air Entrainment by Plunging Water Jets

2002 ◽  
Vol 37 (3) ◽  
pp. 599-612 ◽  
Author(s):  
Tamer Bagatur ◽  
Ahmet Baylar ◽  
Nusret Sekerdag
Keyword(s):  
Penetration Depth ◽  
Oxygen Transfer ◽  
Free Water ◽  
Air Entrainment ◽  
Water Jet ◽  
Transfer Efficiency ◽  
Entrainment Rate ◽  
Water Jets ◽  
Air Entrainment Rate ◽  
Oxygen Transfer Efficiency

Abstract In this study, for the plunging water jet aeration system using various inclined nozzle types, bubble penetration depth, air entrainment rate, water jet expansion, effect of water jet circumference at impact point, oxygen transfer coefficient and oxygen transfer efficiency which changed depending on the water jet velocity, were researched in an air-water system. Numerous studies were conducted with circular nozzles. The present study describes new experiments performed with different nozzle types. Three types of nozzles were examined, i.e., those with circular, ellipse and rectangle duct with rounded ends. Experimental results showed that water jets produced with ellipse and rectangle duct with rounded ends nozzles have very different flow characteristics, entrainment patterns on free water jet surface, and submerged water jet region within the receiving tank. Higher air entrainment rate and oxygen transfer efficiency was observed in the rectangle duct with rounded ends nozzle due to water jet expansion. Bubble penetration depth, however, is lower for the rectangle duct with rounded ends nozzle than for the other nozzles. The ellipse nozzle provided the highest bubble penetration depth. These results showed that it is appropriate to use ellipse nozzle in aeration of deep pool and rectangle duct with rounded ends nozzle in the applications where high bubble concentration is desirable.

scholarly journals Oxygenation by Hollow Plunging Water Jet

1970 ◽  
Vol 7 (1) ◽  
pp. 40-47 ◽  
Author(s):  
Surinder Deswal
Keyword(s):  
Transfer Coefficient ◽  
Oxygen Transfer ◽  
Water System ◽  
Water Jet ◽  
Transfer Efficiency ◽  
Oxygen Transfer Coefficient ◽  
Water Jets ◽  
Oxygen Transfer Efficiency ◽  
Plunging Water Jet ◽  
Volumetric Oxygen Transfer Coefficient

Oxygenation by a plunging water jet is a more attractive way to effect oxygen-transfer than conventional oxygenation systems. A lot of work has been reported on the oxygen-transfer by plunging water jets. However, few studies have been carried out on hollow plunging jet. In this paper, volumetric oxygen-transfer coefficient and oxygen-transfer efficiency has been studied experimentally for hollow plunging jet in a pool of water for different thicknesses of jets. This research suggests that the volumetric oxygen-transfer coefficient and oxygen-transfer efficiency of the hollow plunging jet for air-water system are competitive with other types of aeration systems. Further, relationships of volumetric oxygen-transfer coefficient with jet power per unit volume and jet parameters are also proposed. The suggested relationships predict the volumetric oxygen-transfer coefficient for hollow plunging water jet within a scatter of ±15%.Key words: hollow plunging jet, oxygenation, volumetric oxygen-transfer coefficient, oxygentransfer efficiency, jet power.Journal of the Institute of Engineering, Vol. 7, No. 1, 2009 July pp. 40-47doi: 10.3126/jie.v7i1.2061

Role of Nozzles with Air Holes in Air Entrainment by a Water Jet

2003 ◽  
Vol 38 (4) ◽  
pp. 785-795 ◽  
Author(s):  
M. Emin Emiroglu ◽  
Ahmet Baylar
Keyword(s):  
Experimental Study ◽  
Nozzle Exit ◽  
Negative Pressure ◽  
Air Entrainment ◽  
Water Jet ◽  
Entrainment Rate ◽  
Air Bubbles ◽  
Air Entrainment Rate ◽  
Plunging Water Jet

Abstract When a water jet impinges a pool of water at rest, air bubbles may be entrained and carried a distance below the pool's surface. This process is called plunging water jet entrainment and aeration. This paper describes an experimental study of the air entrainment rate of circular nozzles with and without air holes, and in particular, the effect of varying numbers and positions of air holes and distance between the location of the air holes and nozzle exit. A negative pressure occurred due to the air holes on the circular nozzles. This phenomenon affected air entrainment. The differences in air entrainment rate were related to changes in the jet shape. It was demonstrated that the air entrainment rates of the circular nozzles with air holes were significantly higher than those of circular nozzles without air holes.

scholarly journals Air entrainment by inclined circular plunging water jets with various impingement heights

2020 ◽  
Vol 20 (8) ◽  
pp. 3478-3486
Author(s):  
Yiyi Ma ◽  
Luchen Zhang ◽  
Yu Yang ◽  
Ping Wei
Keyword(s):  
Experimental Study ◽  
Surface Roughness ◽  
Water Surface ◽  
Jet Impingement ◽  
Air Entrainment ◽  
Entrainment Rate ◽  
Water Jets ◽  
Air Entrainment Rate ◽  
Jet Breakup ◽  
Early Increase

Abstract This paper presents an experimental study on air entrainment by inclined circular plunging water jets issued from long nozzles with various jet impingement heights up to 6.1 m. Particular attention was paid to the jets having a large impingement height, and which disintegrated into small droplets before reaching the water surface. The dominant sizes and velocities of the droplets generated by jet breakup were 1–4 mm and 4–9 m/s. The results show that for plunging water jets having the same hydraulic head, the air entrainment rate increased as the jet impingement height at first grew, then dropped as the jet impingement height kept increasing. The early increase in the air entrainment rate was due to the growth of jet surface roughness, while the later decrease was caused by the water jet disintegration. The momentum of the plunging jet decreased dramatically due to the reduced mass and the significant energy dissipation through the atmosphere caused by jet disintegration. This led to a much smaller penetration depth and air entrainment rate compared to with a continuous jet.

Acoustic measurements of air entrainment by a plunging free water jet

1999 ◽  
Vol 105 (2) ◽  
pp. 1254-1255
Author(s):  
Thomas R. Hahn ◽  
Thomas K. Berger ◽  
Michael J. Buckingham
Keyword(s):  
Free Water ◽  
Air Entrainment ◽  
Water Jet ◽  
Acoustic Measurements

Oxygen Transfer Efficiency Measurements Using Off-Gas Techniques

1989 ◽  
Vol 21 (10-11) ◽  
pp. 1295-1300 ◽  
Author(s):  
W. C. Boyle ◽  
B. G. Hellstrom ◽  
L. Ewing
Keyword(s):  
Oxygen Uptake ◽  
Uptake Rate ◽  
Oxygen Transfer ◽  
Oxygen Uptake Rate ◽  
Transfer Efficiency ◽  
Theoretical Development ◽  
Process Conditions ◽  
Uptake Rates ◽  
Oxygen Transfer Efficiency ◽  
On Line

The off-gas technique for measuring oxygen transfer efficiency in aeration tanks under process conditions was proposed as an accurate technique for calibrating or verifying on-line methods used to estimate oxygen uptake rates. The theoretical development of the off-gas technique was presented. Application of this technique in verifying or calibrating existing on-line methods for estimating oxygen uptake rate was presented. Direct application as an on-line method for estimating oxygen uptake rate was also discussed.

Experience with Ceramic Plate Diffusers in Large Activated Sludge Plants

1992 ◽  
Vol 25 (4-5) ◽  
pp. 127-134
Author(s):  
R. Warriner ◽  
T. C. Rooney
Keyword(s):  
Activated Sludge ◽  
Oxygen Transfer ◽  
Cost Effective ◽  
Transfer Efficiency ◽  
Ceramic Plate ◽  
Flat Plates ◽  
Higher Power ◽  
Oxygen Transfer Efficiency ◽  
Basin Floor ◽  
The Difference

Fine pore aeration systems were evaluated in a U.S.EPA sponsored study of oxygen transfer efficiency in 26 activated sludge plants. Two plants in the study, those of the Milwaukee Metropolitan Sewerage District, had aeration systems composed of flat plates grouted into containers placed flush with the basin floor. The remaining plants in the study had aeration systems utilizing various disk, dome, and tube devices that are now in far more widespread use than the flat plates. The District's aeration basins gave better oxygen transfer efficiency than the other ceramic diffuser systems studied. The difference may have been the result of the high tank area to diffuser area ratio and the low air flux rates associated with the plate systems. At one MMSD plant there were also four basins with recently installed ceramic disk diffuser systems. This provided an opportunity for side-by-side comparisons between the disks and the flat plates in containers. An analysis of diffuser system first costs and energy costs indicated that the ceramic plate system could be cost effective at higher power costs, but not at the prices presently paid by the District for power.

Study of Air Bubble Formation for Wastewater Treatment

2011 ◽  
Author(s):  
Bryan A. Miletta ◽  
R. S. Amano ◽  
Ammar A. T. Alkhalidi ◽  
Jin Li
Keyword(s):  
Wastewater Treatment ◽  
Oxygen Transfer ◽  
Surface Membrane ◽  
Bubble Formation ◽  
High Oxygen ◽  
Transfer Efficiency ◽  
Intimate Contact ◽  
Rubber Membrane ◽  
Unit Process ◽  
Oxygen Transfer Efficiency

Aeration, a unit process in which air and water are brought into intimate contact, is an extremely important step in the process of wastewater treatment. The two most common systems of aeration are subsurface and mechanical. A mechanical system agitates the wastewater by various means (e.g. paddles, blades, or propellers) to introduce air from the atmosphere. Subsurface aeration is the release of air, in the form of bubbles, within the tank of wastewater to supply the microorganisms with the required amount of oxygen they need to metabolize and break down the organic material suspended in the wastewater. The bubbles of Air are released from the bottom of the wastewater tank through diffusers. These diffusers have a surface membrane, usually made of punched rubber, to create the fine bubbles with high oxygen transfer efficiency from supplied air to the diffusers. Since the energy crisis in the early 1970’s, there has been increased interest in these systems due to its high oxygen transfer efficiency. This paper covers experimentation of different air diffuser membranes, varying in material, used in the aeration process of wastewater treatment. Rubber, EPDM rubber (ethylene-propylene-diene Monomer) and PTFE Polytetrafluoroethylene membranes coated membranes were tested. Experimental results showed that the rubber membrane produced the smallest bubble size against expectation. This could be a result of the coating being on the top surface only and the bubble starts from inside the punch.

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