An Experimental Study of Air Entrainment and Oxygen Transfer at a Water Jet from a Nozzle with Air Holes

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.

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An experimental study of nozzle diameters, aeration depths and angles on standard aeration efficiency (SAE) in a venturi aerator

Water Practice & Technology ◽

10.2166/wpt.2009.043 ◽

2009 ◽

Vol 4 (3) ◽

Cited By ~ 1

Author(s):

M.R. Ghomi ◽

M. Sohrabnejad ◽

M. R. Ovissipour

Keyword(s):

Experimental Study ◽

Oxygen Transfer ◽

Air Entrainment ◽

Nozzle Diameter ◽

Venturi Tube ◽

Water Pump ◽

Significant Difference ◽

Oxygen Transfer Efficiency ◽

Aeration Efficiency ◽

Nozzle Size

A 1.1 kW submersible water pump with a venturi air injector was used in this study to examine the effects of three factors including nozzle diameter (14, 17 and 20 mm), aeration depth (20, 40 and 60 cm), and aeration angle (0, 22.5 and 45°) on standard aeration efficiency (SAE). For maximum air entrainment, HT / DT ratio and DT / DN ratio were equal to zero and 2, respectively. Among the first factor experiments, 14 mm nozzle diameter showed the highest SAE value (P<0.05). Although, 60 cm aeration depth and 45° aeration angle had more SAE value among other depths and angles, but there was not a significant difference (P>0.05) in each aeration depths and angles. Only, the determination coefficient for effect of nozzle diameters on SAE value showed a good result (R2= 0.958). The greatest oxygen transfer efficiency in this study has been achieved with using 14 mm nozzle size, 60 cm depth of aeration, and 45° angle of venturi tube in water aeration that was 1.166 kgO2/ kWh. Venturi aerators are very inexpensive in comparison with other aerators and have some other advantages that can be considered as one of the best devices for water aeration.

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

Water Quality Research Journal ◽

10.2166/wqrj.2003.049 ◽

2003 ◽

Vol 38 (4) ◽

pp. 785-795 ◽

Cited By ~ 6

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.

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