Abstract: A computational fluid dynamics simulation is done for
non-Newtonian fluid in a baffled stirred tank. The CMC solution is
taken as non-Newtonian shear thinning fluid for simulation. The
Reynolds Average Navier Stocks equation with steady state multi
reference frame approach is used to simulate flow in the stirred tank.
The turbulent flow field is modelled using realizable k-ε turbulence
model. The simulated velocity profiles of Rushton turbine is
validated with literature data. Then, the simulated flow field of CD-6
impeller is compared with the Rushton turbine. The flow field
generated by CD-6 impeller is less in magnitude than the Rushton
turbine. The impeller global parameter, power number and flow
number, and entropy generation due to viscous dissipation rate is also
reported.
Abstract: This study was conducted to evaluate the manganese
removal from aqueous solution using Banana peels activated carbon
(BPAC). Batch experiments have been carried out to determine the
influence of parameters such as pH, biosorbent dose, initial metal ion
concentrations and contact times on the biosorption process. From
these investigations, a significant increase in percentage removal of
manganese 97.4% is observed at pH value 5.0, biosorbent dose 0.8 g,
initial concentration 20 ppm, temperature 25 ± 2°C, stirring rate 200
rpm and contact time 2h. The equilibrium concentration and the
adsorption capacity at equilibrium of the experimental results were
fitted to the Langmuir and Freundlich isotherm models; the Langmuir
isotherm was found to well represent the measured adsorption data
implying BPAC had heterogeneous surface. A raw groundwater
samples were collected from Baharmos groundwater treatment plant
network at Embaba and Manshiet Elkanater City/District-Giza,
Egypt, for treatment at the best conditions that reached at first phase
by BPAC. The treatment with BPAC could reduce iron and
manganese value of raw groundwater by 91.4% and 97.1%,
respectively and the effect of the treatment process on the
microbiological properties of groundwater sample showed decrease
of total bacterial count either at 22°C or at 37°C to 85.7% and 82.4%,
respectively. Also, BPAC was characterized using SEM and FTIR
spectroscopy.
Abstract: During welding, the amount of heat present in weld
zones determines the quality of weldment produced. Thus, the heat
distribution characteristics and its magnitude in weld zones with
respect to process variables such as tool pin-shoulder rotational and
traveling speed during welding is analyzed using thermal finite
element analyses method. For this purpose, transient thermal finite
element analyses are performed to model the temperatures
distribution and its quantities in weld-zones with respect to process
variables such as rotational speed and traveling speed during welding.
Commercially available software Altair HyperWork is used to model
three-dimensional tool pin-shoulder vs. workpieces and to simulate
the friction stir process. The results show that increasing tool
rotational speed, at a constant traveling speed, will increase the
amount of heat generated in weld-zones. In contrary, increasing
traveling speed, at constant tool pin-shoulder rotational speeds, will
reduce the amount of heat generated in weld zones.
Abstract: Fly ash is an important waste, produced in thermal
power plants which causes very important environmental pollutions.
For this reason the usage and evaluation the fly ash in various areas
are very important. Nearly, 15 million tons/year of fly ash is
produced in Turkey. In this study, usage of fly ash with diatomite and
molasses for heavy metal (Cd) adsorption from wastewater is
investigated. The samples of Seyitomer region fly ash were analyzed
by X-ray fluorescence (XRF) and Scanning Electron Microscope
(SEM) then diatomite (0 and 1% in terms of fly ash, w/w) and
molasses (0-0.75 mL) were pelletized under 30 MPa of pressure for
the usage of cadmium (Cd) adsorption in wastewater. After the
adsorption process, samples of Seyitomer were analyzed using
Optical Emission Spectroscopy (ICP-OES). As a result, it is seen that
the usage of Seyitomer fly ash is proper for cadmium (Cd) adsorption
and an optimum adsorption yield with 52% is found at a compound
with Seyitomer fly ash (10 g), diatomite (0.5 g) and molasses (0.75
mL) at 2.5 h of reaction time, pH:4, 20ºC of reaction temperature and
300 rpm of stirring rate.
Abstract: In this study, a liquid phase microextraction by hollow fiber (HF-LPME) combined with high performance liquid chromatography-UV detector was applied to preconcentrate and determine trace levels of Cyproheptadine in human urine and plasma samples. Cyproheptadine was extracted from 10 mL alkaline aqueous solution (pH: 9.81) into an organic solvent (n-octnol) which was immobilized in the wall pores of a hollow fiber. Then was back-extracted into an acidified aqueous solution (pH: 2.59) located inside the lumen of the hollow fiber. This method is simple, efficient and cost-effective. It is based on pH gradient and differences between two aqueous phases. In order to optimize the HF-LPME some affecting parameters including the pH of donor and acceptor phases, the type of organic solvent, ionic strength, stirring rate, extraction time and temperature were studied and optimized. Under optimal conditions enrichment factor, limit of detection (LOD) and relative standard deviation (RSD(%), n=3) were up to 112, 15 μg.L−1 and 2.7, respectively.
Abstract: This study compared the mechanical and microstructural properties produced during friction stir welding (FSW) of S275 structural steel in air and underwater. Post weld tests assessed the tensile strength, micro-hardness, distortion, Charpy impact toughness and fatigue performance in each case. The study showed that there was no significant difference in the strength, hardness or fatigue life of the air and underwater specimens. However, Charpy impact toughness was shown to decrease for the underwater specimens and was attributed to a lower degree of recrystallization caused by the higher rate of heat loss experienced when welding underwater. Reduced angular and longitudinal distortion was observed in the underwater welded plate compared to the plate welded in air.
Abstract: SiC reinforced Aluminum samples were produced by stir casting of liquid AA1200 aluminum alloy at 600-650ºC casting temperature. 83µm SiC particles were rinsed in 10g/l, 20g/l and 30g/l molar concentration of Sncl2 through cleaning times of 0, 60, 120, and 180 minutes. Some cast samples were tested for mechanical properties and some were subjected to heat treatment before testing. The SnCl2 rinsed SiC reinforced aluminum exhibited higher yield strength, hardness, stiffness and elongation which increases with cleaning concentration and time up to 120 minutes, compared to composite with untreated SiC. However, the impact energy resistance decreases with cleaning concentration and time. The improved properties were attributed to good wettability and mechanical adhesion at the fiber-matrix interface. Quenching and annealing the composite samples further improve the tensile/yield strengths, elongation, stiffness, hardness similar to those of the as-cast samples.
Abstract: 12.7-mm thick plates of 6061-T6511 aluminum alloy and high hardness steel (528 HV) were successfully joined by a friction stir bonding process using a tungsten-rhenium stir tool. Process parameter variation experiments, which included tool design geometry, plunge and traverse rates, tool offset, spindle tilt, and rotation speed, were conducted to develop a parameter set which yielded a defect free joint. Laboratory tensile tests exhibited yield stresses which exceed the strengths of comparable AA6061-to-AA6061 fusion and friction stir weld joints. Scanning electron microscopy and energy dispersive X-ray spectroscopy analysis also show atomic diffusion at the material interface region.
Abstract: Nonlinearity is the inherent characteristics of all the industrial processes. The Classical control approach used for a generation often fails to show better results particularly for non-linear systems and in the systems, whose parameters changes over a period of time for a variety of reasons. Alternatively, adaptive control strategies provide very good performance. The Model Reference Adaptive Control based on Lyapunov stability analysis and classical PI control strategies are designed and evaluated for Continuous Stirred Tank Reactor, which shows appreciable dynamic nonlinear characteristics.
Abstract: In this project three type of tools, straight cylindrical, taper cylindrical and triangular tool all made of High speed steel (Wc-Co) used for the friction stir welding (FSW) aluminum alloy H20–H20 and the mechanical properties of the welded joint tested by tensile test and vicker hardness test. Besides, mentioned mechanical properties compared with each other to make conclusion. The result helped design of welding parameter optimization for different types of friction stir process like rotational speed, depth of welding, travel speed, type of material, type of joint, work piece dimension, joint dimension, tool material and tool geometry. Previous investigations in different types of materials work pieces; joint type, machining parameter and preheating temperature take placed. In this investigation 3 mentioned tool types that are popular in FSW tested and the results completed other aspects of the process. Hope this paper can open a new horizon in experimental investigation of mechanical properties for friction stir welded joint with other different type of tools like oval shape probe, paddle shape probe, three flat sided probe, and three sided re-entrant probe and other materials and alloys like titanium or steel in near future.
Abstract: The speed profiles, gas holdup (eG) and global oxygen transfer coefficient (kLa) from a stirred airlift bioreactor using water as the fluid model, was investigated by computational fluid dynamics modeling. The parameters predicted by the computer model were validated with the experimental dates. The CFD results were very close to those obtained experimentally. During the simulation it was verified a prevalent impeller effect at low speeds, propelling a large volume of fluid against the walls of the vessel, which without recirculation, results in low values of eG and kLa; however, by increasing air velocity, the impeller effect is smaller with the air flow being greater, in the region of the riser, causing fluid recirculation, which explains the increase in eG and kLa.
Abstract: Stirred tanks are widely used in all industrial sectors. The need for further studies of the mixing operation and its different aspects comes from the diversity of agitation tools and implemented geometries in addition to the specific characteristics of each application. Viscous fluids are often encountered in industry and they represent the majority of treated cases, as in the polymer sector, food processing, pharmaceuticals and cosmetics. That's why in this paper, we will present a three-dimensional numerical study using the software Fluent, to study the effect of varying the fluid viscosity in a stirred tank with a Rushton turbine. This viscosity variation was performed by adding carboxymethylcellulose (CMC) to the fluid (water) in the vessel. In this work, we studied first the flow generated in the tank with a Rushton turbine. Second, we studied the effect of the fluid viscosity variation on the thermodynamic quantities defining the flow. For this, three viscosities (0.9% CMC, 1.1% CMC and 1.7% CMC) were considered.
Abstract: Metal matrix composites consists of a metallic matrix combined with dispersed particulate phase as reinforcement. Aluminum alloys have been the primary material of choice for structural components of aircraft since about 1930. Well known performance characteristics, known fabrication costs, design experience, and established manufacturing methods and facilities, are just a few of the reasons for the continued confidence in 7XXX Al alloys that will ensure their use in significant quantities for the time to come. Particulate MMCs are of special interest owing to the low cost of their raw materials (primarily natural river sand here) and their ease of fabrication, making them suitable for applications requiring relatively high volume production. 7XXX Al alloys are precipitation hardenable and therefore amenable for thermomechanical treatment. Al–Zn alloys reinforced with particulate materials are used in aerospace industries in spite of the drawbacks of susceptibility to stress corrosion, poor wettability, poor weldability and poor fatigue resistance. The resistance offered by these particulates for the moving dislocations impart secondary hardening in turn contributes strain hardening. Cold deformation increases lattice defects, which in turn improves the properties of solution treated alloy. In view of this, six different Al–Zn–Mg alloy composites reinforced with silica (3 wt. % and 5 wt. %) are prepared by conventional semisolid synthesizing process. The cast alloys are solution treated and aged. The solution treated alloys are further severely cold rolled to enhance the properties. The hardness and strength values are analyzed and compared with silica free Al – Zn-Mg alloys. Precipitation hardening phenomena is accelerated due to the increased number of potential sites for precipitation. Higher peak hardness and lesser aging time are the characteristics of thermo mechanically treated samples. For obtaining maximum hardness, optimum number and volume of precipitate particles are required. The Al-5Zn-1Mg with 5% SiO2 alloy composite shows better result.
Abstract: The design of temperature measuring approach for a re-configured milling machine to produce friction stir welds is reported in this paper. The product design specifications for the redesigning of a milling machine were first outlined and the ranking criteria were determined. Three different concepts were generated for the temperature measurement on the reconfigured system and the preferred or the best concept was selected based on the set design ranking criteria. Further simulation and performance analysis was then conducted on the concept. The Infrared Thermography (IRT) concept was selected for the temperature measurement among other concepts generated because it is an ideal and most effective system of measurement in this regard.
Abstract: Microbial depyritization of coal using chemoautotrophic bacteria is gaining acceptance as an efficient and eco-friendly technique. The process uses the metabolic activity of chemoautotrophic bacteria in removing sulfur and pyrite from the coal. The aim of the present study was to investigate the potential of Acidithiobacillus ferrooxidans in removing the pyritic sulfur and iron from high iron and sulfur containing US coal. The experiment was undertaken in 8L bench scale stirred tank reactor having 1% (w/v) pulp density of coal. The reactor was operated at 35ºC and aerobic conditions were maintained by sparging the air into the reactor. It was found that at the end of bio-depyritization process, about 90% of pyrite and 67% of pyritic sulfur was removed from the coal. The results indicate that the bio-depyritization process is an efficient process in treating the high pyrite and sulfur containing coal.
Abstract: Different approaches for heating\cooling of stirred tanks, coils and jackets, are investigated using computational fluid dynamics (CFD).A time-dependant sliding mesh approach is applied to simulate the flow in both conditions. The investigations are carried out under the turbulent flow conditions for a Rushton impeller and heating elements are considered isothermal. The flow behavior and temperature distribution are studied for each case and heat transfer coefficient is calculated. Results show different velocity profiles for each case. Unsteady temperature distribution is not similar for different cases .In the case of the coiled stirred vessel more uniform temperature and higher heat transfer coefficient is resulted.
Abstract: Electron back-scattered diffraction was used to follow the evolution of microstructure from the base metal to the stir zone (SZ) in a duplex stainless steel subjected to friction stir welding. In the stir zone (SZ), a continuous dynamic recrystallization (CDRX) was evidenced for ferrite, while it was suggested that a static recrystallization together with CDRX may occur for austenite. It was found that ferrite and austenite grains in the SZ take a typical shear texture of bcc and fcc materials respectively.
Abstract: The direct synthesis process of dimethyl ether (DME)
from syngas in slurry reactors is considered to be promising because
of its advantages in caloric transfer. In this paper, the influences of
operating conditions (temperature, pressure and weight hourly space
velocity) on the conversion of CO, selectivity of DME and methanol
were studied in a stirred autoclave over Cu-Zn-Al-Zr slurry catalyst,
which is far more suitable to liquid phase dimethyl ether synthesis
process than bifunctional catalyst commercially. A Langmuir-
Hinshelwood mechanism type global kinetics model for liquid phase
DME direct synthesis based on methanol synthesis models and a
methanol dehydration model has been investigated by fitting our
experimental data. The model parameters were estimated with
MATLAB program based on general Genetic Algorithms and
Levenberg-Marquardt method, which is suitably fitting experimental
data and its reliability was verified by statistical test and residual
error analysis.
Abstract: This article demonstrated development of
controlled release system of an NSAID drug, Diclofenac
sodium employing different ratios of Ethyl cellulose.
Diclofenac sodium and ethyl cellulose in different proportions
were processed by microencapsulation based on phase
separation technique to formulate microcapsules. The
prepared microcapsules were then compressed into tablets to
obtain controlled release oral formulations. In-vitro evaluation
was performed by dissolution test of each preparation was
conducted in 900 ml of phosphate buffer solution of pH 7.2
maintained at 37 ± 0.5 °C and stirred at 50 rpm. At predetermined
time intervals (0, 0.5, 1.0, 1.5, 2, 3, 4, 6, 8, 10, 12,
16, 20 and 24 hrs). The drug concentration in the collected
samples was determined by UV spectrophotometer at 276 nm.
The physical characteristics of diclofenac sodium
microcapsules were according to accepted range. These were
off-white, free flowing and spherical in shape. The release
profile of diclofenac sodium from microcapsules was found to
be directly proportional to the proportion of ethylcellulose and
coat thickness. The in-vitro release pattern showed that with
ratio of 1:1 and 1:2 (drug: polymer), the percentage release of
drug at first hour was 16.91 and 11.52 %, respectively as
compared to 1:3 which is only 6.87 % with in this time. The
release mechanism followed higuchi model for its release
pattern. Tablet Formulation (F2) of present study was found
comparable in release profile the marketed brand Phlogin-SR,
microcapsules showed an extended release beyond 24 h.
Further, a good correlation was found between drug release
and proportion of ethylcellulose in the microcapsules.
Microencapsulation based on coacervation found as good
technique to control release of diclofenac sodium for making
the controlled release formulations.
Abstract: This study demonstrates the feasibility of joining the commercial pure copper plates by friction stir welding (FSW). Microstructure, microhardness and tensile properties in terms of the joint efficiency were found 94.03 % compare to as receive base material (BM). The average hardness at the top was higher than bottom. Hardness of weld zone was higher than the base material. Different microstructure zones were revealed by optical microscopy and scanning electron microscopy. The stirred zone (SZ) exhibited primary two phases namely, recrystallized grains and fine precipitates in matrix of copper.