scholarly journals The Influence of Impeller Geometry on the Gas Bubbles Dispersion in Uro-200 Reactor – RTD Curves / Wpływ Rodzaju Wirnika Na Dyspersję Pęcherzyków Gazowych W Reaktorze URO-200 – Krzywe Mieszania

2015 ◽  
Vol 60 (4) ◽  
pp. 2887-2894 ◽  
Author(s):  
M. Saternus ◽  
T. Merder ◽  
J. Pieprzyca
Keyword(s):  
Flow Rate ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Gas Bubbles ◽  
Refining Process ◽  
Inert Gas ◽  
Impeller Speed ◽  
Batch Reactors ◽  
Liquid Aluminium ◽  
Impeller Geometry

URO-200 reactor belongs to batch reactors used in refining process of aluminium and its alloys in polish foundries. The appropriate level of hydrogen removal from liquid aluminium can be obtained when the mixing of inert gas bubbles with liquid metal is uniform. Thus, the important role is played by the following parameters: flow rate of refining gas, geometry of the impeller, rotary impeller speed. The article presents the results of research conducted on physical model of URO-200 reactor. The NaCl tracer was introduced to water (modelling liquid aluminium) and then the conductivity was measured. Basing on the obtained results the Residence Time Distribution (RTD) curves were determined. The measurements were carried out for two different rotary impellers, flow rate equaled 5, 10, 15 and 20 dm3/min and rotary impeller speed from 250 to 400 rpm every 50 rpm.

Effects of wetland depth and flow rate on residence time distribution characteristics

2004 ◽  
Vol 23 (3) ◽  
pp. 189-203 ◽  
Author(s):  
Jeff F. Holland ◽  
Jay F. Martin ◽  
Timothy Granata ◽  
Virginie Bouchard ◽  
Martin Quigley ◽  
...  
Keyword(s):  
Residence Time ◽  
Flow Rate ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Distribution Characteristics

scholarly journals Optimization of a Continuous Hybrid Impeller Mixer via Computational Fluid Dynamics

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
N. Othman ◽  
S. K. Kamarudin ◽  
M. S. Takriff ◽  
M. I. Rosli ◽  
E. M. F. Engku Chik ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Operating Conditions ◽  
Impeller Speed ◽  
Transient Condition ◽  
Experimental Investigations ◽  
Rushton Turbine

This paper presents the preliminary steps required for conducting experiments to obtain the optimal operating conditions of a hybrid impeller mixer and to determine the residence time distribution (RTD) using computational fluid dynamics (CFD). In this paper, impeller speed and clearance parameters are examined. The hybrid impeller mixer consists of a single Rushton turbine mounted above a single pitched blade turbine (PBT). Four impeller speeds, 50, 100, 150, and 200 rpm, and four impeller clearances, 25, 50, 75, and 100 mm, were the operation variables used in this study. CFD was utilized to initially screen the parameter ranges to reduce the number of actual experiments needed. Afterward, the residence time distribution (RTD) was determined using the respective parameters. Finally, the Fluent-predicted RTD and the experimentally measured RTD were compared. The CFD investigations revealed that an impeller speed of 50 rpm and an impeller clearance of 25 mm were not viable for experimental investigations and were thus eliminated from further analyses. The determination of RTD using ak-εturbulence model was performed using CFD techniques. The multiple reference frame (MRF) was implemented and a steady state was initially achieved followed by a transient condition for RTD determination.

Mixing and Residence Time Distribution in an Inert Gas-Shrouded Tundish

2016 ◽  
Vol 48 (1) ◽  
pp. 17-21 ◽  
Author(s):  
Saikat Chatterjee ◽  
Amjad Asad ◽  
Christoph Kratzsch ◽  
Rüdiger Schwarze ◽  
Kinnor Chattopadhyay
Keyword(s):  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Inert Gas

Mixing and Heat Transfer in Helical Capillary Flow Reactors With Alternating Bends

2014 ◽  
Author(s):  
Marius G. Gelhausen ◽  
Safa Kutup Kurt ◽  
Norbert Kockmann
Keyword(s):  
Heat Transfer ◽  
Chemical Reactions ◽  
Residence Time ◽  
Flow Rate ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Capillary Flow ◽  
Exothermic Reaction ◽  
Small Diameter ◽  
Wall Material

Capillary flow is often occurring in natural and technical systems. Due to small diameter channels, laminar flow is established, while heat transfer is high from large specific surface area. For chemical reactions, good mixing and a narrow residence time distribution are important for high selectivity and yield. To improve mixing and residence time distribution, several measures of bend flow, helical arrangements and curved capillaries are proposed in literature. This contribution describes the flow, residence time distribution, and its influence on chemical reactions in short helical, alternating reactor capillaries (SHARC). The influence of the number of bends between alternating coils on the residence time distribution is described for different capillary and coil diameter, coil length and flow rate in laminar regime. The residence time distribution is a good measure for axial mixing and dispersion, while the heat transfer is mainly affected by the flow rate. The SHARC device was built from polymer capillaries of fluorinated ethylene propylene (FEP, inner diameter of 0.38 and 0.75 mm) with high mechanical flexibility for bending and good chemical resistance. Despite of low heat conductivity of the wall material, volumetric heat transfer coefficients of more than 5 MW/m3K were measured in a water bath. A highly exothermic reaction with adiabatic temperature increase of more than 100 K could be operated without detecting reaction runaway.

scholarly journals Physical Modelling of Aluminum Refining Process Conducted in Batch Reactor with Rotary Impeller

Metals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 726 ◽  
Author(s):  
Mariola Saternus ◽  
Tomasz Merder
Keyword(s):  
Liquid Metal ◽  
Flow Rate ◽  
Batch Reactor ◽  
Physical Modelling ◽  
Processing Parameters ◽  
Refining Process ◽  
Impeller Speed ◽  
Water Model ◽  
Aluminum Production ◽  
Gas Dispersion

The refining process is one of the essential stages of aluminum production. Its main aim is to remove hydrogen, that causes porosity and weakens the mechanical and physical properties of casting aluminum. The process is mainly conducted by purging inert gas through the liquid metal, using rotary impellers. The geometry of the impellers and the processing parameters, such as flow rate of gas and rotary impeller speed, influence the gas dispersion level, and therefore the efficiency of the process. Improving the process, and optimization of parameters, can be done by physical modelling. In this paper, the research was carried out with the use of a water model of batch reactor, testing three different rotary impellers. Varied methods were used: visualization, which can help to evaluate the level of dispersion of gas bubbles in liquid metal; determination of residence time distribution (RTD) curves, which was obtained by measuring the conductivity of NaCl tracer in the fluid; and indirect studies, completed by measuring the content of dissolved oxygen in water to simulate hydrogen desorption. The research was carried out for different processing parameters, such as flow rate of refining gas (5–25 L·min−1) and rotary impeller speed (3.33–8.33 s−1). The obtained results were presented graphically and discussed in detail.

Slurry Utilization Efficiency Studies in Chemical Mechanical Planarization

2003 ◽  
Vol 767 ◽  
Author(s):  
Ara Philipossian ◽  
Erin Mitchell
Keyword(s):  
Residence Time ◽  
Flow Rate ◽  
Surface Texture ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Chemical Mechanical Planarization ◽  
Operating Conditions ◽  
Utilization Efficiency ◽  
Slurry Flow ◽  
Slurry Flow Rate

AbstractThe residence time distribution of slurry in the pad-wafer interface was experimentally determined and used to calculate the slurry utilization efficiency (η) of the CMP process. Slurry utilization efficiency represents the percentage of slurry that actually participates in the polish by entering the region bounded between the wafer and the pad. Results show that η ranges from 2 to 22 percent, depending on operating conditions such as applied wafer pressure, relative pad wafer velocity, slurry flow rate and pad surface texture (i.e. type of pad grooving).

Fission Gas Bubbles in Fractured UO2

1968 ◽  
Vol 26 ◽  
pp. 286-287
Author(s):  
O. M. Katz
Keyword(s):  
Electron Microscopy ◽  
Thermal Gradient ◽  
Gas Bubbles ◽  
Inert Gas ◽  
Thermal Gradients ◽  
Fission Gas ◽  
Beam Heating ◽  
Limited Application ◽  
Bubble Characteristics ◽  
Electron Beam Heating

The swelling of irradiated UO2 has been attributed to the migration and agglomeration of fission gas bubbles in a thermal gradient. High temperatures and thermal gradients obtained by electron beam heating simulate reactor behavior and lead to the postulation of swelling mechanisms. Although electron microscopy studies have been reported on UO2, two experimental procedures have limited application of the results: irradiation was achieved either with a stream of inert gas ions without fission or at depletions less than 2 x 1020 fissions/cm3 (∼3/4 at % burnup). This study was not limited either of these conditions and reports on the bubble characteristics observed by transmission and fractographic electron microscopy in high density (96% theoretical) UO2 irradiated between 3.5 and 31.3 x 1020 fissions/cm3 at temperatures below l600°F. Preliminary results from replicas of the as-polished and etched surfaces of these samples were published.

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