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An experimental-based numerical simulation of two phase flow through porous media: A comparative study on finite element and finite difference schemes
, Article Petroleum Science and Technology ; Volume 31, Issue 18 , 2013 , Pages 1881-1890 ; 10916466 (ISSN) ; Kharrat, R ; Ghazanfari, M. H ; Sharif University of Technology
2013
Abstract
In this study, the nonlinear partial differential equations governing two phase flow through porous media are solved using two different methods, namely, finite difference and finite element. The capillary pressure term is considered in the mathematical model. The numerical results on a 2-D test case are then compared with the experimental drainage process and water flooding performed on a glass type micromodel. Based on the obtained results, finite difference technique needs less computational time for solving governing equations of two phase flow, but findings of this method show less agreement with the experimental data. The finite element scheme was found to be more adequate and its...
Prediction of asphaltene precipitation during solvent/CO2 injection conditions: A comparative study on thermodynamic micellization model with a different characterization approach and solid model
, Article Journal of Canadian Petroleum Technology ; Vol. 50, issue. 3 , March , 2011 , p. 65-74 ; Masihi, M ; Ghazanfari, M. H ; Kharrat, R ; Sharif University of Technology
2011
Abstract
There are different thermodynamic models that have been applied for modelling of asphaltene precipitation caused by various reasons, such as solvent/CO2 injection and pressure depletion. In this work, two computer codes based on two different asphaltene precipitation thermodynamic models-the first being the thermodynamic micellization model with a different characterization approach and the second being the solid model-have been developed and used for predicting asphaltene precipitation data reported in the literature as well as in the obtained data for Sarvak reservoir crude, which is one of the most potentially problematic Iranian heavy oil reserves under gas injection conditions. For the...
Phase behavior modeling of asphaltene precipitation for heavy crude including the effect of pressure and temperature
, Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Vol. 36, issue. 19 , Feb , 2014 , p. 2087-2094 ; ISSN: 15567036 ; Ghazanfari, M. H ; Masihi, M ; Kharrat, R ; Sharif University of Technology
2014
Abstract
Despite numerous experimental and modeling studies, the role of temperature changes on phase behavior modeling of asphaltene precipitation and, in consequence, developing of asphaltene phase envelope in heavy crudes, remains a topic of debate in the literature. In this work, a computer code based on the non-isothermal improved solid model has been developed and used for predicting asphaltene precipitation data for one of the Iranian heavy crudes at different levels of temperature and pressure. The parameters of the non-isothermal model were tuned using three onset pressures at three different temperatures, and the asphaltene phase envelope was developed. The results showed that at high...
Prediction of asphaltene precipitation during pressure depletion and CO2 injection for heavy crude
, Article Petroleum Science and Technology ; Vol. 28, issue. 9 , Mar , 2009 , p. 892-902 ; ISSN: 10916466 ; Kharrat, R ; Masihi, M ; Ghazanfari, M. , H ; Sharif University of Technology
2009
Abstract
In this work, a thermodynamic approach is used for modeling the phase behavior of asphaltene precipitation. The precipitated asphaltene phase is represented by an improved solid model, and the oil and gas phases are modeled with an equation of state. The Peng-Robinson equation of state (PR-EOS) was used to perform flash calculations. Then, the onset point and the amount of precipitated asphaltene were predicted. A computer code based on the solid model was developed and used for predicting asphaltene precipitation data reported in the literature as well as the experimental data obtained from high-pressure, high-temperature asphaltene precipitation experiments performed on Sarvak reservoir...
Prediction of asphaltene precipitation during solvent/CO2 injection conditions: A comparative study on thermodynamic micellization model with a different characterization approach and solid model
, Article Journal of Canadian Petroleum Technology ; Volume 50, Issue 3 , 2011 , Pages 65-74 ; 00219487 (ISSN) ; Masihi, M ; Ghazanfari, M. H ; Kharrat, R ; Sharif University of Technology
2011
Abstract
There are different thermodynamic models that have been applied for modelling of asphaltene precipitation caused by various reasons, such as solvent/CO2 injection and pressure depletion. In this work, two computer codes based on two different asphaltene precipitation thermodynamic models-the first being the thermodynamic micellization model with a different characterization approach and the second being the solid model-have been developed and used for predicting asphaltene precipitation data reported in the literature as well as in the obtained data for Sarvak reservoir crude, which is one of the most potentially problematic Iranian heavy oil reserves under gas injection conditions. For the...
An improvement of thermodynamic micellization model for prediction of asphaltene precipitation during gas injection in heavy crude
, Article Fluid Phase Equilibria ; Volume 308, Issue 1-2 , September , 2011 , Pages 153-163 ; 03783812 (ISSN) ; Masihi, M ; Ghazanfari, M. H ; Kharrat, R ; Sharif University of Technology
2011
Abstract
Thermodynamic micellization model is known as an appropriate approach for prediction of asphaltene precipitation. However, the reliability (i.e. accuracy) of this model for whole range of pressure or injected gas mole percent must be checked. In practice, the accuracy can be improved by using a suitable characterization method. In this research, a computer code for implementing the thermodynamic micellization model has been developed. Having used this program, we make the prediction of asphaltene precipitation by using data reported in the literature as well as the experimental data obtained from high pressure, high temperature asphaltene precipitation experiments under gas injection...
Prediction of asphaltene precipitation during pressure depletion and CO2 injection for heavy crude
, Article Petroleum Science and Technology ; Volume 28, Issue 9 , Apr , 2010 , Pages 892-902 ; 10916466 (ISSN) ; Kharrat, R ; Masihi, M ; Ghazanfari, M. H ; Sharif University of Technology
2010
Abstract
In this work, a thermodynamic approach is used for modeling the phase behavior of asphaltene precipitation. The precipitated asphaltene phase is represented by an improved solid model, and the oil and gas phases are modeled with an equation of state. The Peng-Robinson equation of state (PR-EOS) was used to perform flash calculations. Then, the onset point and the amount of precipitated asphaltene were predicted. A computer code based on the solid model was developed and used for predicting asphaltene precipitation data reported in the literature as well as the experimental data obtained from high-pressure, high-temperature asphaltene precipitation experiments performed on Sarvak reservoir...
Bragg reflector for optical high voltage sensor applications
, Article Integrated Optical Devices: Fabrication and Testing, Brugge, 30 October 2002 through 1 November 2002 ; Volume 4944 , 2002 , Pages 287-292 ; 0277786X (ISSN) ; Mehrany, K ; Rashidian, B ; Tavakkoli, A ; SPIE ; Sharif University of Technology
2002
Abstract
Optical measurement of voltage because of its excellent advantages is studied by several research groups. In this paper, two optically voltage measurement method based on periodic structure have been introduced. First one is based on Bragg reflection effect. The coefficient of reflection from a periodic layered medium depends on properties of periodic structure. In this work a periodic structure on LiNbO3 substrate was considered and under a high voltage electric field perpendicular to surface of layers, refractive indices of substrate have been changed. Performance of reflection versus applied electric field was calculated. Second method was based on Guided-mode resonance effect. Guided...
Phase behavior modeling of asphaltene precipitation for heavy crudes: A promising tool along with experimental data
, Article International Journal of Thermophysics ; Vol. 33, issue. 12 , December , 2012 , p. 2251-2266 ; ISSN: 0195928X ; Kharrat, R ; Masihi, M ; Ghazanfari, M. H ; Fadaei, S ; Sharif University of Technology
2012
Abstract
Thermodynamic modeling is known as a promising tool for phase behavior modeling of asphaltene precipitation under different conditions such as pressure depletion and CO2 injection. In this work, a thermodynamic approach is used for modeling the phase behavior of asphaltene precipitation. The precipitated asphaltene phase is represented by an improved solid model, while the oil and gas phases are modeled with an equation of state. The PR-EOS was used to perform flash calculations. Then, the onset point and the amount of precipitated asphaltene were predicted. A computer code based on an improved solid model has been developed and used for predicting asphaltene precipitation data for one of...
Phase behavior modeling of asphaltene precipitation for heavy crudes: A promising tool along with experimental data
, Article International Journal of Thermophysics ; Volume 33, Issue 12 , December , 2012 , Pages 2251-2266 ; 0195928X (ISSN) ; Kharrat, R ; Masihi, M ; Ghazanfari, M. H ; Fadaei, S ; Sharif University of Technology
2012
Abstract
Thermodynamic modeling is known as a promising tool for phase behavior modeling of asphaltene precipitation under different conditions such as pressure depletion and CO2 injection. In this work, a thermodynamic approach is used for modeling the phase behavior of asphaltene precipitation. The precipitated asphaltene phase is represented by an improved solid model, while the oil and gas phases are modeled with an equation of state. The PR-EOS was used to perform flash calculations. Then, the onset point and the amount of precipitated asphaltene were predicted. A computer code based on an improved solid model has been developed and used for predicting asphaltene precipitation data for one of...
Synthesis of Double Network Hydrogels Based on Chitosan, Alginate, and Poly (Vinyl Alchohol) with High Mechanical Properties and Investigation of Their Biocompatibility
, M.Sc. Thesis Sharif University of Technology ; Pourjavadi, Ali (Supervisor)
Abstract
Double network (DN) hydrogels are a new interpenetrate polymer network (IPN) that are usually contain about 60-90 % water. Despite of this amount of water, they are though and strong. DN hydrogels comprise of two networks, the first one as the brittle gel, is generally high density crosslinked and the second one, the loose and stretchable network, is loosely crosslinked or even without crosslinking. Therefore, we used cationic polymer, chitosan, and anionic polymer, alginate, as the first networks, therefore, we used sodium phosphate for physical crosslinking of chitosan, and calcium chloride as the physical crosslinking agents for alginate network. Also, poly (vinyl alcohol) (PVA), as the...
Production of Sn Base Composite Solder Reinforced by Nanoparticles Via Melt-spinning Technique
, M.Sc. Thesis Sharif University of Technology ; Tavakkoli, Rouhollah (Supervisor)
Abstract
Lead-containing solder alloys in particular Sn-37Pb is the most common alloy used in electronics industry, this alloy has the good mechanical properties and excellent wetting properties and low prices. Recently, increasing environmental and health concerns over the toxicity of lead combined with strict legislation to ban the use of lead-based solders have provided an inevitable driving force for the development of lead-free solder alloys. A group of these lead-free solders are nanocomposite solders that because of having the reinforcement nano particles exhibit lots of unique properties, such as good mechanical and thermal properties. The aim of this research produce a new tin base...
Effect of Remelting Processes on Microstructure and Segregation in Inconel-100 Superalloys Produced by VIM
, M.Sc. Thesis Sharif University of Technology ; Tavakkoli, Ruhollah (Supervisor)
Abstract
In the present work, the effect of different methods of melting, remelting and solidification conditions on the microstructural evolution of IN100 superalloy was investigated. For this purpose, the superalloy was solidified within steel and ceramic molds to provide different cooling rates. Furthermore, the re-melting processes using ESR in the water circulated copper mold and ceramic molds, VAR and combined ESR and VAR were considered. The microstructure of alloy under different casting and remelting conditions were studied by means of optical and SEM microscopy and ESD analysis. According to our results, the ingot which was cast in the ceramic molds, due to lower cooling rate during...
Optimal Design of Parting Line in the Shape Casting Processes
, M.Sc. Thesis Sharif University of Technology ; Tavakkoli, Rouhollah (Supervisor)
Abstract
More than 70 weight percentage of using parts in diverse industries (such as military, civil, automobile productions and etc.) are produceed by the casting processes. For each one of the casting procceses, mold cavity is requisite for arrived molten metal in the mold cavity to get eventuated as a solidified part. Based on mold ilk, if the mold is permanent, the cast part must be capable to be remoeved from the the mold inside. For the non-permanent mold (asssuming multi-piece and non-monolithic), if the model requires to be removed from the mold inside after molding and before casting, only model (no cast part) has to be moldable (why for removing the solidified cast part from the...
Ultrasound dosimetery using microbubbles
, Article IFMBE Proceedings, 20 June 2011 through 23 June 2011 ; Volume 35 IFMBE , June , 2011 , Pages 359-362 ; 16800737 (ISSN) ; 9783642217289 (ISBN) ; Zahedi, E ; Tavakkoli, J ; Sharif University of Technology
2011
Abstract
In this paper, a new technique based on nonlinear resonance of microbubbles is investigated in order to estimate the amplitude of an ultrasound wave pressure field. First, the existing theoretical model is reviewed. Then, an experimental setup consisting of a bubble generator and transmitting/receiving ultrasound transducers operating in the 1 MHz frequency range is described. The effect of background noise is also taken into account. Results show that the second harmonic oscillations are detectable, paving the way to develop a quantitative method for in vivo calibration of ultrasound waves
Effect of molybdenum on grain boundary segregation in Incoloy 901 superalloy
, Article Materials and Design ; Volume 46 , 2013 , Pages 573-578 ; 02641275 (ISSN) ; Abbasi, S. M ; Sharif University of Technology
2013
Abstract
In this paper, the effect of molybdenum on the grain boundary segregation of other elements was studied in Incoloy 901 superalloy. Initially, five alloys were prepared with different percentages of Mo by using a vacuum induction furnace. Then, these alloys were remelted by Electro-slag remelting (ESR) process and after homogenizing at 1160 °C for 2. h followed by air cooling, were rolled. The effect of Mo on segregation of elements was evaluated with Scanning Electron Microscopy, Linear Analysis, and the mechanical tests. The results showed that the grain boundary segregations of elements in Incoloy 901 superalloy were decreased by increasing of molybdenum content up to 6.7% and the...
Design and evaluation of a TNA explosive-detection system to screen carry-on luggage
, Article Journal of Radioanalytical and Nuclear Chemistry ; Volume 248, Issue 3 , 2001 , Pages 695-697 ; 02365731 (ISSN) ; Mireshghi, S. A ; Sharif University of Technology
2001
Abstract
Thermal neutron analysis (TNA) technology has been used for the non-destructive detection of explosives. The system uses a relatively weak 252Cf neutron source (1.03.107 n/s) and two 3″3×″ NaI(Tl) detectors. The presence of explosives is confirmed via detection of the 10.83 MeV prompt gamma-ray associated with nitrogen decay. The MCNP4A code was used to simulate the neutron and gamma transport through the system. The thermal neutron flux in the activation position was measured using gold and indium foils. The measured thermal neutron flux was lower, by not more than 9.5%, than that of simulation. In this report the results of the preliminary tests on the system are described
Implementation of Virtual Structure Approach in Multiple Spacecraft Formation Flight Using Visual Sensors
, M.Sc. Thesis Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
In this research, it has been trying to implement Virtual Structure method for formation flight of multiple spacecraft. In this method, a virtual solid frame with virtual center of mass is considered and agents are arranged in a formation with respect to the virtual center. In this work, a formation keeping control system is implemented in which a feedback from formation to virtual structure and vice versa is considered. The method is implemented firstly in a nongradient field and then developed into a circular orbit in order to investigate the in-orbital effects. An algorithm for collision avoidance, based on relative distances and relative velocities, was also developed. The algorithm was...
An Investigation of Brittle Fracture of Composite Pressure Vessels with Metal Liner Using a Numerical Approach Based on XFEM
, M.Sc. Thesis Sharif University of Technology ; Hosseini Kordkhili, Ali (Supervisor)
Abstract
A metal cylinder tank with composite coating is a pressure vessel which is made of a thin metal layer and a composite layer; like Graphite, and most of the loading is carried by the composite layer. In this study the penny-shaped cracks in cylindrical pressure vessels with composite coating is studied. These kinds of cracks are mostly initiated in manufacturing processes and they have crucial rule in fatigue life and load carrying of the structure. Although there are numerous analytical and numerical methods, they have shortcomings in the case of penny-shaped cracks problems. The strain discontinuity in the interfaces of materials along with discontinuity and singularity due to the crack are...
Model Predictive Orbit Control of a LEO Satellite Using Gauss’s Variational Equations
, M.Sc. Thesis Sharif University of Technology ; Asadian, Nima (Supervisor)
Abstract
In comparison to attitude control of a satellite which is widely used in practical missions, orbit control (espescialy autonomous orbit control) has been only recently paid attention. Autonomous, on-board orbit control, also called autonomous stationkeeping, means the automatic maintenance of all of orbital elements by the satellite itself. In this thesis, an autonomous absolute orbit control strategy for a single Low Earth Orbit (LEO) satellite is presented. When the satellite violates the control trigger error limits, then the controller is activated and calculates a sequence of orbital maneuvers that move the satellite towards its desired states. The absolute orbit control of the...