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Study on Continuous Phase Holdup in a Pulsed Disc and Doughnut Extraction Column by Radiotracer Technique
, M.Sc. Thesis Sharif University of Technology ; Outokesh, Mohammad (Supervisor) ; Tabasi, Mohsen (Supervisor) ; Mostaedi, M.T (Co-Advisor)
Abstract
The dispersed phase holdup is one of the important parameters in the design pulsed column and set the column diameter, height and characteristics of flooding and mass transfer. High efficiency and low space requirements of these columns cause is particularly in the nuclear industry, Due to the possible presence of radiation and the need for protection against radiation, considered and used. In this project, the dispersed phase holdup and mean residence time in a pulsed disc and donut column in a semi-industrial scale using radiotracer and shut down methods compared and presented for water-kerosene system. Also axial dispersion coefficient in the column using radiotracer methods is calculated...
The Effect of Sea Current on an Artificial Island
, M.Sc. Thesis Sharif University of Technology ; Abbaspour Tehrani Fard, Majid (Supervisor)
Abstract
With regards to rapid growth of world population, coastlines have limited natural resources and capacity for human settlement. To tackle the problem the idea of constructing artificial islands could be a solution. Since the artificial islands are semi-enclosed body of water designed to attract not only tourists but also settlements, the flow current pattern and residence time of water should be studied in detail in order to ensure adequate water quality in the surrounding area. In this study, an artificial island is planned to be constructed around Kish Island in Persia Gulf. In this article the effects of different geometries on circulation and residence time of water are investigated...
The Effects of Residence Time, Temperature and Particle size in Partially Reduction of Hematite to Magnetite VIA Fluidized bed Furnace
, M.Sc. Thesis Sharif University of Technology ; Halai, Mohammad (Supervisor)
Abstract
The Effects of temperature, residence time and particle size has been investigated on partial reduction of hematite to magnetite VIA fluidized bed reactor. Since there is water crisis in Iran, it is not rational to use gravity separation processes. Rather the best way is to use magnetic separation. Ghazvin’s region non-coking coal was used for gasifying step in various temperatures in order to produce the gas reduction agent. Golgohr’s mine waste concentrate were tested as the initial iron ore. For the very first time, the residence time of the particles were investigated by the change of height of reaction chamber, in 3 different heights, and the highest i.e. 15 cm had the best results. As...
Investigation of the Effect of Asphaltene on the Stability of Water-oil Emulsion
, M.Sc. Thesis Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Baghban Salehi, Mahsa (Supervisor) ; Masihi, Mohsen (Supervisor)
Abstract
During the production of crude oil from reservoirs, the production of quantities of formation water along with this oil, causes the crude oil does not have the necessary indicators for transportation, refining and ultimately export. The presence of water and salt along with crude oil causes corrosion of refinery and transmission equipment and makes oil unfavorable in terms of economic efficiency (both for domestic use and for export). water and salt produce stable emulsion with oil that can be stable for a long time and can not be easily separated from crude oil. Therefore, separation of water and salt from crude oil is one of the most important issues in the oil industry. Breaking this...
Hydrodynamic Analysis of Fuel Motion in a Binary Bubbling Fluidized Bed using Markov Chains Method
, M.Sc. Thesis Sharif University of Technology ; Fotovat, Farzam (Supervisor)
Abstract
One of the main challenges in managing flow batteries usage is estimating their state of charge. Since The concentration of ions in the battery indicates the battery's charge and, on the other hand, the sensors for measuring the concentration are expensive, observers should be used to estimate the concentrations of the ions in the battery. This work is done by measuring the cell voltage, and finally, using the mathematical model of the battery, the amount of concentrations and state of charge is calculated. In this work, a vanadium flow battery was initially modeled accurately and mechanistically using COMSOL software to replace an actual flow battery in subsequent studies. Also, two...
Application of a continuous kinetic model for the hydrocracking of vacuum gas oil
, Article Petroleum Science and Technology ; Vol. 32, Issue. 18 , 2014 , Pages 2245-2252 ; ISSN: 10916466 ; Khorasheh, F ; Farhadi, F ; Sharif University of Technology
Abstract
Hydrocracking is one of the most versatile petroleum refining processes for production of valuable products including gasoline, gas oil, and jet fuel. In this paper, a five-parameter continuous lumping model was used for kinetic modeling of hydrocracking of vacuum gas oil (VGO). The model parameters were estimated from industrial data obtained from a fixed bed reactor operating at an average temperature of 400°C and residence time of 0.3 h. Product distributions were obtained in terms of the weight fraction of various boiling point cuts. The model parameters were estimated using the Nelder-Mead optimization procedure and were correlated with temperature. Comparison of experimental and...
Effect of empty bed residence time on biotrickling filter performance: Case study-triethylamine
, Article International Journal of Environmental Science and Technology ; Vol. 11, issue. 1 , 2014 , pp. 183-190 ; ISSN: 17351472 ; Bayat, R ; Keshavarzi Shirazi, H ; Sotoudeheian, S ; Sharif University of Technology
Abstract
In this study, a laboratory-scale biotrickling filter (BTF) is used to remove Triethylamine (TEA) from gaseous wastes. The BTF is made of stainless steel with a height of 210 cm and an internal diameter of 21 cm packed with lava rocks. TEA elimination pattern was evaluated by changing empty bed residence times (EBRTs). The maximum elimination capacity (EC) has been determined to be 87 g/m3/h. At all EBRTs 52, 31, 20, and 10 s, contaminant transferring from gas phase to liquid was more than the EC. Also, the removal efficiency was 100 % for a mass loading of 100 g/m3/h. While the liquid recirculation velocity of 3.466 m3/m2/h was maintained, the flow rate was adjusted to 60, 100, 156, and 312...
The joint reaction of methanol and i-butane over the HZSM-5 zeolite
, Article Journal of Industrial and Engineering Chemistry ; Volume 19, Issue 3 , May , 2013 , Pages 915-919 ; 1226086X (ISSN) ; Kazemeini, M ; Mohammadrezaee, A ; Golhosseini, R ; Sharif University of Technology
2013
Abstract
The effects of i-butane addition to methanol in MTP reaction were investigated over an in-house prepared HZSM-5 catalyst. It was observed that, propylene yield would be enhanced when i-butane fed to the reactor along with methanol. The rising growth of the propylene yield continued to peak on till the balance in thermal condition established. Similar trends have been observed when water was added to the mixture. The effect of WHSV with fixed water composition on product distribution was also studied. The optimum point where the highest amount of propylene yielded was shown to be high depended upon the temperature and residence time
Numerical investigation of cone angle effect on the flow field and separation efficiency of deoiling hydrocyclones
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 49, Issue 2 , February , 2013 , Pages 247-260 ; 09477411 (ISSN) ; Maddahian, R ; Farhanieh, B ; Sharif University of Technology
2013
Abstract
In this study, the effect of cone angle on the flow field and separation efficiency of deoiling hydrocyclones is investigated taking advantage of large eddy simulation. The dynamic Smagorinsky is employed to determine the residual stress tensor of the continuous phase. The method of Lagrangian particle tracking with an optimized search algorithm (closest cell) is applied to evaluate the separation efficiency of deoiling hydrocyclone. Simulations are performed on a 35-mm deoiling hydrocyclone with the three different cone angles of 6, 10 and 20 degree. The numerical results revealed that the changes in the cone angle would affect the velocity and pressure distribution inside hydrocyclone, and...
Experimental study of forced circulation evaporator in zero discharge desalination process
, Article Desalination ; Volume 285 , January , 2012 , Pages 352-358 ; 00119164 (ISSN) ; Mowla, D ; Jafari Nasr, M. R ; Soltanieh, M ; Sharif University of Technology
Abstract
Zero discharge desalination process is the most promising technology to prevent salinity and thermal shocks to ecosystem by effluent streams of desalination unit drained into the sea. Pretreatment, solar pond and forced circulation crystallizer are the major steps of one option to provide the purposes of zero discharge desalination process. Reduction of total hardness of wastewater occurs in pretreatment unit and the solar pond is proposed for effluent concentrated brine wastewater of pretreatment unit which seeks production of potable water and concentrated brine. The effluent stream from solar pond is conveyed to one forced circulation evaporator in order to produce salt and distilled...
Direct conversion of methane to methanol over v 2O 5/Sio 2 catalyst in a fixed-bed reactor utilizing a CFD model
, Article World Academy of Science, Engineering and Technology ; Volume 73 , 2011 , Pages 797-802 ; 2010376X (ISSN) ; Morteza, S ; Fattahi, M ; Sharif University of Technology
Abstract
A dynamic model of oxidation of methane to methanol has been developed in a fixed-bed reactor applying V2O5/SiO2 as the reaction catalyst. The standard k-? model with 10% turbulence amount performed. The effects of temperature (450- 500°C) and pressure (20-120 bar) with residence time of 3 seconds, on methane conversion and methanol or formaldehyde selectivity examined. Oxygen used as an oxidant and the amount of oxygen in feed was 5% mol/mol of methane amount. The results showed with increasing the conversion of methane from 0.66 to 1.52%, the selectivity to methanol decreased from 93.4% to 91.9%. The CFD modeling results showed reasonable agreement with the obtained experimental data of...
Evaluation and modeling of a newly designed impinging stream photoreactor equipped with a TiO2 coated fiberglass cloth
, Article RSC Advances ; Volume 5, Issue 12 , 2015 , Pages 9019-9027 ; 20462069 (ISSN) ; Mohammadi, M. M ; Sohrabi, M ; Royaee, S. J ; Sharif University of Technology
Royal Society of Chemistry
2015
Abstract
The photocatalytic degradation of p-nitrophenol (PNP) using TiO2 particles immobilized on a fiberglass cloth was investigated in a novel design of a photo-impinging stream reactor. A spray painted method has been used for the coating process. The structural properties of the immobilized sample were examined using X-ray diffraction and a scanning electron microscope (SEM). The photocatalytic degradation results showed the good performance of the reactor. The flow regime within the reactor was characterized and modeled by applying a liquid residence time distribution. A compartment model consisting of four continuous stirred regions was assigned to describe the flow pattern in the reactor. A...
CFD Simulation of hydrodynamic of a bubble column reactor operating in churn-turbulent regime and effect of gas inlet distribution on system characteristics
, Article International Journal of Chemical Reactor Engineering ; Volume 14, Issue 1 , 2016 , Pages 213-224 ; 15426580 (ISSN) ; Zarkesh, J ; Rashtchian, D ; Anvari, A ; Sharif University of Technology
Walter de Gruyter GmbH
Abstract
CFD simulation of cylindrical bubble column including air as dispersed phase and water as continuous phase operating in churn-turbulent flow regime with diameter of 0.49 m, height of 3.6 m and gas superficial velocity of 0.14 m/s have been conducted. All simulations have been carried out in a 2D axisymmetric, unsteady and Euler/Euler framework with the aid of commercial software FLUENT v. 14.5. Simulations were validated by our experimental results through residence time distribution (RTD) data. Effect of bubble size distribution at inlet on column hydrodynamic was investigated and results clearly showed that equilibrium bubble size distribution in most parts of column is independent of...
Aerosol nano-particle charger simulations and optimizations
, Article Scientia Iranica ; Volume 23, Issue 5 , 2016 , Pages 2220-2229 ; 10263098 (ISSN) ; Saidi, M. S ; Sani, M ; Sharif University of Technology
Sharif University of Technology
Abstract
Size distribution of aerosol particles is prevalently obtained through electrical characterization techniques and study of charged particles' dynamics in the presence of electric field. In this work, a wire-cylinder corona charger is presented, redesigned, and aero dynamically optimized. An initial 2D axisymmetric geometry of the charger was employed for the simulations using the Computational Fluid Dynamics (CFD) commercial code FLUENT 6.3.26. Through successive attempts, a new geometry was obtained by streamlining the walls to eliminate the undesired vortices produced in the flow field of the previous ones. The process optimized the charger by minimizing losses and dilutions of the...
Numerical study of pollutant emissions in a Jet stirred reactor under elevated pressure Lean premixed conditions
, Article Mathematical Problems in Engineering ; Volume 2016 , 2016 ; 1024123X (ISSN) ; Shakeri, A ; Sharif University of Technology
Hindawi Publishing Corporation
2016
Abstract
Numerical study of pollutant emissions (NO and CO) in a Jet Stirred Reactor (JSR) combustor for methane oxidation under Elevated Pressure Lean Premixed (EPLP) conditions is presented. A Detailed Flow-field Simplified Chemistry (DFSC) method, a low computational cost method, is employed for predicting NO and CO concentrations. Reynolds Averaged Navier Stokes (RANS) equations with species transport equations are solved. Improved-coefficient five-step global mechanisms derived from a new evolutionary-based approach were taken as combustion kinetics. For modeling turbulent flow field, Reynolds Stress Model (RSM), and for turbulence chemistry interactions, finite rate-Eddy dissipation model are...
Fluid–structure interaction simulation of a cerebral aneurysm: effects of endovascular coiling treatment and aneurysm wall thickening
, Article Journal of the Mechanical Behavior of Biomedical Materials ; Volume 74 , 2017 , Pages 72-83 ; 17516161 (ISSN) ; Nejad, M. A ; Saeedi, M ; Sharif University of Technology
Abstract
In the present study, we investigate the effect of the hemodynamic factors of the blood flow on the cerebral aneurysms. To this end, a hypothetical geometry of the aneurysm in the circle of Willis, located in the bifurcation point of the anterior cerebral artery (ACA) and anterior communicating artery (ACoA) is modeled in a three-dimensional manner. Three cases are chosen in the current study: an untreated thin wall (first case), untreated thick wall (second case), and a treated aneurysm (third case). The effect of increasing the aneurysm wall thickness on the deformation and stress distribution of the walls are studied. The obtained results showed that in the second case, a reduction in the...
Triethylamine removal using biotrickling filter (BTF): effect of height and recirculation liquid rate on BTFs performance
, Article International Journal of Environmental Science and Technology ; Volume 14, Issue 8 , 2017 , Pages 1615-1624 ; 17351472 (ISSN) ; Sotoudeheian, S ; Bayat, R ; Sharif University of Technology
Center for Environmental and Energy Research and Studies
2017
Abstract
This study investigated the removal of triethylamine using a biotrickling filter. The influence of affecting parameters, such as height and recirculation liquid rate (VL) on contaminant removal efficiency, was examined in detail. The results demonstrated that in the constant empty bed residence time (EBRT), when VL was increased, the removal efficiency (RE) increased. Also, for a specific VL, increasing EBRT could also increase RE values. However, it seems that an increasing VL is a more cost-effective way to enhance RE as compared to an increasing EBRT. The obtained outcomes represented that for a constant EBRT, an increase in inlet loading (IL) could decrease RE. For lower ILs, the removal...
Exploring source water mixing and transient residence time distributions of outflow and evapotranspiration with an integrated hydrologic model and Lagrangian particle tracking approach
, Article Ecohydrology ; 2018 ; 19360584 (ISSN) ; Condon, L. E ; Danesh Yazdi, M ; Bearup, L. A ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
Understanding the time water takes as it moves from rain or snowmelt through the terrestrial system to arrive as stream discharge, or evapotranspiration (ET) is an important hydrologic quantity. We develop a Lagrangian particle tracking method to capture transient residence times from source to either ET or outflow in an integrated hydrologic model. This method is parallel and efficiently captures time evolution of parcels of water in the model and tracks the source of water for hydrograph or ET separation. We demonstrate this model using hypothetical hillslope simulations driven by snow or rain dominated forcing and two different land cover types. We show that land cover and forcing both...
Igniter jet dynamics in solid fuel ramjets
, Article Acta Astronautica ; Volume 64, Issue 2-3 , 2009 , Pages 166-175 ; 00945765 (ISSN) ; Farshchi, M ; Sharif University of Technology
2009
Abstract
The dynamics of a two dimensional plane jet injected at the base of a step, parallel to the wall, in backward facing step flow geometry is numerically studied. The objective of this work is to gain insight into the dynamics of the igniter flow field in solid fuel ramjet motors. Solid fuel ramjets operate by ingestion of air and subsequent combustion with a solid fuel grain such as polyethylene. The system of governing equations is solved with a finite volume approach using a structured grid in which the AUSM+ scheme is used to calculate the convective fluxes. The Spalart and Allmaras turbulence model is used in these simulations. Experimental data have been used to validate the flow solver...
Photocatalytic degradation of furfural by titania nanoparticles in a floating-bed photoreactor
, Article Chemical Engineering Journal ; Volume 146, Issue 1 , 2009 , Pages 79-85 ; 13858947 (ISSN) ; Vossoughi, M ; Borghei, M ; Sharif University of Technology
2009
Abstract
In this research, an attempt was made to investigate the potential of nanophotocatalysts for treatment of hazardous wastewater streams. Titanium dioxide nanoparticles (as photocatalyst) were immobilized on a porous and low-density support called "perlite" using a very simple and inexpensive method. TiO2-coated perlite granules were used in a "Floating-bed photoreactor" to study the photocatalytic purification process of a typical wastewater polluted by furfural. The effects of initial concentration, catalyst mass/solution volume ratio, oxidant molar flow, residence time, and light intensity on process removal efficiency, and kinetics of the reactions were studied. SEM analyses showed a...