scholarly journals Auto-Aspirated DAF Sparger Study on Flow Hydrodynamics, Bubble Generation and Aeration Efficiency

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1498
Author(s):  
Dmitry Vladimirovich Gradov ◽  
Andrey Saren ◽  
Janne Kauppi ◽  
Kari Ullakko ◽  
Tuomas Koiranen
Keyword(s):  
Size Distribution ◽  
Water Flow ◽  
Flow Rate ◽  
Bubble Size ◽  
Transfer Rate ◽  
Pure Water ◽  
Water Flow Rate ◽  
Bubble Size Distribution ◽  
Bubble Generation ◽  
Aeration Efficiency

A novel auto-aspirated sparger is examined experimentally in a closed-loop reactor (CLR) at lab scale using particle image velocimetry, high-speed camera and oxygen mass transfer rate measurements. State-of-the-art 3D printing technology was utilized to develop the sparger design in stainless steel. An insignificant change in the bubble size distribution was observed along the aerated flow, proving the existence of a low coalescence rate in the constraint domain of the CLR pipeline. The studied sparger created macrobubbles evenly dispersed in space. In pure water, the produced bubble size distribution from 190 to 2500 μm is controlled by liquid flow rate. The bubble size dynamics exhibited a power-law function of water flow rate approaching a stable minimum bubble size, which was attributed to the ratio of the fast-growing energy of the bubble surface tension over the kinetic energy of the stream. Potentially, the stream energy can efficiently disperse higher gas flow rates. The oxygen transfer rate was rapid and depended on the water flow rate. The aeration efficiency below 0.4 kW/m3 was superior to the commonly used aerating apparatuses tested at lab scale. The efficient gas dissolution technology has potential in water treatment and carbon capture processes applications.

Micro-scale simulation of bubble-water flow in coal seams by the lattice Boltzmann method

2016 ◽  
Vol 56 (2) ◽  
pp. 608
Author(s):  
Jie Yi ◽  
Huilin Xing ◽  
Tianwei Sun ◽  
Victor Rudolph
Keyword(s):  
Coal Seam ◽  
Water Flow ◽  
Flow Rate ◽  
Bubble Size ◽  
Lattice Boltzmann ◽  
Water Flow Rate ◽  
Bubble Flow ◽  
Coal Seam Gas ◽  
Two Phase ◽  
Flow Process

The production of coal seam gas initially requires pumping and removing significant amounts of water to sufficiently reduce the hydrostatic pressure in the subsurface, so that methane can desorb from the matrix and diffuse into the cleat systems; majority of the methane molecules gather into nucleation or bubbles. During the depression, the flow pattern of gas in cleats changes from bubble flow to slug flow, and finally forms circular flow. The significance of the bubble flow process—during which the liquid phase is continuous while the gas phase exists as small bubbles randomly distributed within the liquid—has not been emphasised because of its complexity. In this study, a free energy based two-phase lattice Boltzmann model is used to simulate the gas bubble/water flow behaviour in micro-cleats of a coal seam gas reservoir. The model was validated by comparison with analytical results based on dimensionless numbers, and good agreement was found in general. The influences of bubble shape, bubble size, and coal surface wettability on gas water two-phase flow in micro-cleats are discussed. The simulation results indicate that the bubble size and wettability of gas have significant impacts on the flow capacity of both gas and water. A decrease of the water flow rate is observed when large bubbles occur, and the gas flow rate decreases when the gas wettability becomes stronger. The bubble flow process significantly influences the drainage of water and the further gas production.

scholarly journals Influence of the Gas Bubble Size Distribution on the Ladle Stirring Process

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1663
Author(s):  
Mengkun Li ◽  
Lintao Zhang
Keyword(s):  
Size Distribution ◽  
Flow Rate ◽  
Bubble Size ◽  
Axial Velocity ◽  
Gas Flow ◽  
Normal Function ◽  
Bubble Size Distribution ◽  
Low Flow ◽  
Gas Bubble ◽  
Log Normal

This work aims at figuring out the influence of gas bubble size distribution on the ladle stirring process. The work is conducted through three-dimensional (3D) numerical simulation based on the finite volume method. Mesh sensitivity test and the cross-validation are performed to ensure the results are mesh independent and the numerical set-up is correct. Two distributions, uniform and Log-normal function, are investigated under different gas flow rates and number of porous plugs. The results indicate that the results, e.g., the axial velocity and the area of the slag eye, have little difference for low flow rate. The difference becomes dominant whilst the flow rate is increasing, such as 600 NL/min. The Log-normal function bubble size distribution gives a larger axial velocity and a smaller slag eye area compared to the uniform bubble size distribution. This work indicated that, at a higher flow rate, the Log-normal function is a better choice to predict the melt behavior and the slag open eye in the ladle refining process if the bubble interaction is not considered.

scholarly journals Oxidation Behavior of Steel With Cr Content and Water Flow Rate

2017 ◽  
Vol 62 (2) ◽  
pp. 1383-1387
Author(s):  
D.-J. Kim ◽  
K.M. Kim ◽  
J.H. Shin ◽  
Y.M. Cheong ◽  
E.H. Lee ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Ion Transport ◽  
Water Flow ◽  
Flow Rate ◽  
Nuclear Power ◽  
Immersion Time ◽  
Oxidation Behavior ◽  
Pure Water ◽  
Water Flow Rate ◽  
Cr Content

AbstractFast water flow facilitates ferrous ion transport leading to flow accelerated corrosion (FAC) of carbon steel and the possibility of a large accident through a failure of a secondary pipe in a nuclear power plant. Ion transport is directly linked to oxide properties such as the thickness, chemical composition and porosity. This work deals with a precise observation of the cross section of the corroded specimen focusing on an oxide passivity and its thickness using SEM (scanning electron microscope) and TEM (transmission electron microscope) as well as an apparent weight loss and a surface observation for the specimens corroded using a rotating cylindrical electrode autoclave system in pure water of pH 7 at 150°C having dissolved oxygen below 1 ppb within a flow rate range of 0 to 10 m/s. The Cr content in steel was changed from 0.02 to 2.4 wt%. Increasing the Cr content in the alloy, the FAC rate and oxide thickness decreased. The oxide porosity tends to decrease with the Cr content and immersion time owing to the development of Cr containing oxide. The oxidation behavior is not changed with the immersion time.

Experimental Study on Bubble Size Distribution in Gas-Liquid Reversed Jet Loop Reactor

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Rongshan Bi ◽  
Jiao Tang ◽  
Linxi Wang ◽  
Qingqing Yang ◽  
Meilan Zuo ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Size Distribution ◽  
Gas Phase ◽  
Flow Rate ◽  
Bubble Size ◽  
Draft Tube ◽  
Bubble Size Distribution ◽  
Image Processing Technique ◽  
Phase Flow ◽  
Loop Reactor

Abstract Bubble size distribution (BSD) is important for gas-liquid jet loop reactor (JLR)’s mass transfer performance of inter-phases. A self-designed reversed JLR was investigated with air-water system on the BSD. The CCD camera of particle imaging velocimetry (PIV) system and image processing technique were used to obtain the reliable photo. The influences of four parameters, gas phase flow rate, liquid phase flow rate, draft tube diameter and ejector mounting position, on the BSD were studied in detail. The results showed that the local BSD is accordance with log-normal distribution under the experimental conditions and the average diameter and BSD range increase with the increase of the gas phase flow rate, and decrease with the increase of the liquid phase flow rate, the downward movement of the nozzle installation position and the increase of the diameter of the draft tube.

New Approach to Quartz Coarse Particles Flotation Using Nanobubbles, with Emphasis on the Bubble Size Distribution

2019 ◽  
Vol 19 (01) ◽  
pp. 1850048
Author(s):  
Sabereh Nazari ◽  
Sied Ziaedin Shafaei ◽  
Mahdi Gharabaghi ◽  
Rahman Ahmadi ◽  
Behzad Shahbazi ◽  
...  
Keyword(s):  
Size Distribution ◽  
Flow Rate ◽  
Bubble Size ◽  
Air Flow ◽  
Bubble Size Distribution ◽  
Impeller Speed ◽  
Coarse Particles ◽  
Air Flow Rate ◽  
Operational Parameters ◽  
Flotation Process

This study investigates the influence of bubble size distribution and operational parameters on the flotation behavior of quartz coarse particles. The parameters evaluated during this study include the different bubble size distribution, air flow rate and impeller speed. Experiments were conducted at three different bubble sizes: 110, 171 and 293[Formula: see text]nm as db(32). Then, the results were compared with common air bubbles of the conventional flotation process. The bubble size distribution was measured using a laser particle size analyzer (LPSA). Results showed that the recovery of [Formula: see text]m particles increased in presence of nano bubbles (NBs) up to 25% compared to the conventional flotation. The maximum recovery of 95.59% was obtained using NBs size of 171[Formula: see text]nm at the impeller speed of 900[Formula: see text]rpm and air flow rate of 30[Formula: see text]l/h. It was also indicated that NBs caused an increasing in flotation recovery for all the samples in any size ranges in comparison with the conventional method.

Towards improved accuracy in modeling aeration efficiency through understanding bubble size distribution dynamics

2018 ◽  
Vol 131 ◽  
pp. 346-355 ◽  
Author(s):  
Andreia Amaral ◽  
Giacomo Bellandi ◽  
Usman Rehman ◽  
Ramiro Neves ◽  
Youri Amerlinck ◽  
...  
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Bubble Size Distribution ◽  
Distribution Dynamics ◽  
Aeration Efficiency ◽  
Improved Accuracy

scholarly journals Effect of Water Flow on Underwater Wet Welded A36 Steel

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 682
Author(s):  
Eko Surojo ◽  
Aziz Harya Gumilang ◽  
Triyono Triyono ◽  
Aditya Rio Prabowo ◽  
Eko Prasetya Budiana ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Water Flow ◽  
Flow Rate ◽  
Water Flow Rate ◽  
Physical And Mechanical Properties ◽  
Shielded Metal Arc Welding ◽  
Effect Of Water ◽  
Bending Effect ◽  
Metal Arc Welding ◽  
A36 Steel

Underwater wet welding (UWW) combined with the shielded metal arc welding (SMAW) method has proven to be an effective way of permanently joining metals that can be performed in water. This research was conducted to determine the effect of water flow rate on the physical and mechanical properties (tensile, hardness, toughness, and bending effect) of underwater welded bead on A36 steel plate. The control variables used were a welding speed of 4 mm/s, a current of 120 A, electrode E7018 with a diameter of 4 mm, and freshwater. The results show that variations in water flow affected defects, microstructure, and mechanical properties of underwater welds. These defects include spatter, porosity, and undercut, which occur in all underwater welding results. The presence of flow and an increased flow rate causes differences in the microstructure, increased porosity on the weld metal, and undercut on the UWW specimen. An increase in water flow rate causes the acicular ferrite microstructure to appear greater, and the heat-affected zone (HAZ) will form finer grains. The best mechanical properties are achieved by welding with the highest flow rate, with a tensile strength of 534.1 MPa, 3.6% elongation, a Vickers microhardness in the HAZ area of 424 HV, and an impact strength of 1.47 J/mm2.

Experimental Characterization of a Modified Airlift Pump

2014 ◽  
Author(s):  
Afshin Goharzadeh ◽  
Keegan Fernandes
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
High Speed ◽  
Water Flow Rate ◽  
High Speed Photography ◽  
Two Phase ◽  
Inner Diameter ◽  
Airlift Pump ◽  
Flow Map ◽  
Churn Flow

This paper presents an experimental investigation on a modified airlift pump. Experiments were undertaken as a function of air-water flow rate for two submergence ratios (ε=0.58 and 0.74), and two different riser geometries (i) straight pipe with a constant inner diameter of 19 mm and (ii) enlarged pipe with a sudden expanded diameter of 19 to 32 mm. These transparent vertical pipes, of 1 m length, were submerged in a transparent rectangular tank (0.45×0.45×1.1 m3). The compressed air was injected into the vertical pipe to lift the water from the reservoir. The flow map regime is established for both configurations and compared with previous studies. The two phase air-water flow structure at the expansion region is experimentally characterized. Pipeline geometry is found to have a significant influence on the output water flow rate. Using high speed photography and electrical conductivity probes, new flow regimes, such as “slug to churn” and “annular to churn” flow, are observed and their influence on the output water flow rate and efficiency are discussed. These experimental results provide fundamental insights into the physics of modified airlift pump.

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