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fattaheian-dehkordi--sajjad
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Ferrofluid flow and heat transfer from a sphere in the presence of nonuniform magnetic fields
, Article Journal of Heat Transfer ; Volume 141, Issue 11 , 2019 ; 00221481 (ISSN) ; Molaei Dehkordi, A ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2019
Abstract
In this article, the effects of nonuniform magnetic fields on the hydrodynamics and heat transfer from a heated sphere to its surrounding ferrofluid flow have been investigated. Kelvin body forces originate from the nonuniformity of the applied magnetic field and can generate the vortices behind the sphere leading to a considerable change in the velocity and temperature fields. The applied magnetic field disturbs the thermal boundary layer and decreases heat-transfer resistance, leading to a significant enhancement in the heat-transfer coefficient. Variations of the local and average Nusselt number value (Nu), separation angle, recirculation length, and drag coefficient were considered to...
The effect of nanoparticles on spontaneous imbibition of brine into initially oil-wet sandstones
, Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Volume 41, Issue 22 , 2019 , Pages 2746-2756 ; 15567036 (ISSN) ; Ghasemi Dehkordi, M ; Sharif University of Technology
Taylor and Francis Inc
2019
Abstract
In this paper, the effect of silica nanoparticles on oil production due to the spontaneous imbibition of brine into oil-wet sandstones has been studied. The imbibed fluids were NaCl 3 wt. % solutions containing various concentrations of nanoparticles and the recovered oil for each solution was compared. The results revealed that nanoparticles yielded more oil recovery. Nanofluid was used after brine imbibition, and the oil recovery increased from 17.8% to 40% while in the case of using the same nanofluid as the first imbibed fluid the oil recovery was 53%. Also, the results indicated that the oil recovery depends on nanoparticle concentrations. © 2019, © 2019 Taylor & Francis Group, LLC
Two-dimensional CFD simulation of chemical reactions in tapered-in and tapered-out fluidized bed reactors
, Article Advanced Powder Technology ; Volume 30, Issue 1 , 2019 , Pages 136-147 ; 09218831 (ISSN) ; Molaei Dehkordi, A ; Sharif University of Technology
Elsevier B.V
2019
Abstract
This article presents a simulation study of tapered-in and tapered-out fluidized bed reactors to investigate the influences of apex angle on the fractional conversion and the pressure drop of the fluidized beds in the presence of two types of chemical reaction with gas volume increase and reduction. The 2D behavior of tapered-in and -out fluidized beds was also compared with a columnar one from fractional conversion and bed pressure drop point of views. To validate the simulation results, the numerical predictions for the expansion ratio and the pressure drop of a tapered fluidized bed were compared with experimental data and good agreement was observed. The obtained simulation results...
Synthesis and polymorph controlling of calcite and aragonite calcium carbonate nanoparticles in a confined impinging-jets reactor
, Article Chemical Engineering and Processing - Process Intensification ; 2020 ; Molaei Dehkordi, A ; Sharif University of Technology
Elsevier B.V
2020
Abstract
In this article, a confined-impinging-jets reactor (CIJR) was designed and tested successfully for the synthesis of calcium carbonate nanoparticles using the reactive precipitation method. The proposed CIJR comprised of two opposed nozzles placed in a cylindrical chamber. Effects of various operating and design parameters such as supersaturation, feed flow rate, nozzle diameter, reactor diameter, operating temperature, and surface-active agents on the mean particle size, particle size distribution, and the polymorphs of calcium carbonate nanoparticles were investigated carefully. By changing the supersaturation, reactor diameter, jets velocity, operating temperature, and the nozzle diameter,...
Reactive absorption in packed bed columns in the presence of magnetic nanoparticles and magnetic field: Modeling and simulation
, Article Journal of Industrial and Engineering Chemistry ; Volume 45 , 2017 , Pages 131-144 ; 1226086X (ISSN) ; Molaei Dehkordi, A ; Sharif University of Technology
Korean Society of Industrial Engineering Chemistry
2017
Abstract
In this article, the influences of ferrofluid and magnetic field on the reactive absorption in packed-bed contactors have been investigated. Because of importance of carbon dioxide emission as a global concern, absorption of carbon dioxide was chosen to investigate these effects. In this regard, multitube approach was applied to model the contactor. The simulation results were validated against experimental data reported in the literature in the absence of nanoparticles and magnetic field and good agreement was obtained. Moreover, influences of various operating conditions on the contactor performance were investigated. It was found that for 3.4 vol.% of magnetic nanoparticles (MNPs), the...
Two-dimensional CFD simulation of chemical reactions in tapered-in and tapered-out fluidized bed reactors
, Article Advanced Powder Technology ; Volume 30, Issue 1 , 2019 , Pages 136-147 ; 09218831 (ISSN) ; Molaei Dehkordi, A ; Sharif University of Technology
Elsevier B.V
2019
Abstract
This article presents a simulation study of tapered-in and tapered-out fluidized bed reactors to investigate the influences of apex angle on the fractional conversion and the pressure drop of the fluidized beds in the presence of two types of chemical reaction with gas volume increase and reduction. The 2D behavior of tapered-in and -out fluidized beds was also compared with a columnar one from fractional conversion and bed pressure drop point of views. To validate the simulation results, the numerical predictions for the expansion ratio and the pressure drop of a tapered fluidized bed were compared with experimental data and good agreement was observed. The obtained simulation results...
Synthesis and polymorph controlling of calcite and aragonite calcium carbonate nanoparticles in a confined impinging-jets reactor
, Article Chemical Engineering and Processing - Process Intensification ; Volume 159 , 2021 ; 02552701 (ISSN) ; Molaei Dehkordi, A ; Sharif University of Technology
Elsevier B.V
2021
Abstract
In this article, a confined-impinging-jets reactor (CIJR) was designed and tested successfully for the synthesis of calcium carbonate nanoparticles using the reactive precipitation method. The proposed CIJR comprised of two opposed nozzles placed in a cylindrical chamber. Effects of various operating and design parameters such as supersaturation, feed flow rate, nozzle diameter, reactor diameter, operating temperature, and surface-active agents on the mean particle size, particle size distribution, and the polymorphs of calcium carbonate nanoparticles were investigated carefully. By changing the supersaturation, reactor diameter, jets velocity, operating temperature, and the nozzle diameter,...
Synthesis and polymorph controlling of calcite and aragonite calcium carbonate nanoparticles in a confined impinging-jets reactor
, Article Chemical Engineering and Processing - Process Intensification ; Volume 159 , 2021 ; 02552701 (ISSN) ; Molaei Dehkordi, A ; Sharif University of Technology
Elsevier B.V
2021
Abstract
In this article, a confined-impinging-jets reactor (CIJR) was designed and tested successfully for the synthesis of calcium carbonate nanoparticles using the reactive precipitation method. The proposed CIJR comprised of two opposed nozzles placed in a cylindrical chamber. Effects of various operating and design parameters such as supersaturation, feed flow rate, nozzle diameter, reactor diameter, operating temperature, and surface-active agents on the mean particle size, particle size distribution, and the polymorphs of calcium carbonate nanoparticles were investigated carefully. By changing the supersaturation, reactor diameter, jets velocity, operating temperature, and the nozzle diameter,...
Separation of Xylene Isomers
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
Xylene isomers have similar boiling points and, therefore, their separation by conventional distillation is not practical. The industrial separation of these isomers is generally performed by adsorption or crystallization processes, which are very energy consuming. In this work, the various methods of the separation of these isomers have been reviewed and the equilibrium adsorption of these components in liquid phase using two commercial types of zeolite including Z-700 and Na-BETA as adsorbent at 15, 25, and 35 oC and an initial concentration range of up to 50 wt% as well as in single and binary solutions was investigated. It was found that Z-700 adsorbent has no selectivity for the binary...
A Method for Detecting Source of Malwares in P2P File Sharing Networks
,
M.Sc. Thesis
Sharif University of Technology
;
Kharrazi, Mehdi
(Supervisor)
Abstract
With the extensive use and the growing popularity of file sharing in peer-to-peer (P2P) networks, the distribution of copyrighted files and the propagation of malwares have also increased. The increasing growth of these crimes multiplies the necessity of forensic investigation in order to detect the offenders. The yet proposed methods have sought to gather some proofs for forensic investigation by the application of some changes in clients’ programs and a constant monitoring of the network. These methods, however, have some limitations which have rendered useless the results of their application in real environments. Moreover, the important issues like the detection of the file source have...
Continuous Synthesis of Silver Chloride Nanoparticles Using a Spinning Disk Reactor
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
Silver chloride nanoparticles (AgCl NPs) have been widely used in various areas such as medicine industry, photographic materials, catalytic materials, pigments, and photochromic materials. Therefore, various studies were conducted for their synthesizes. In the present work, precipitation or reactive crystallization method was used for the synthesis of AgCl NPs. In this regard, silver nitrate and sodium chloride as reactants and gelatin as a surfactant were used in a continuous spinning disk reactor (SDR) at the ambient temperature and pressure. The influences of various parameters such as initial supersaturation , free ion ratio, dilution with water , disk diameter , disk rotation speed,...
Theoretical and Experimental Study of Gas-Solid Fluidized Beds Dpm Approach
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
Because of the importance of gas-solid fluidized beds in industrial plants, many efforts have been done for predicting their behavior up to now. Generally, there are two major attitudes for describing and simulating the hydrodynamics of fluidized beds, Eulerian-Eulerian methods and Eulerian-Lagrangian metods. Both of these approaches have their own advantages and disadvantages and a lot of studies have been done to understand the nature of gas-solid fluidized beds with aid of these models. Due to fewer presumptions in the basic structure of Eulerian-Lagrangian methods such as DEM in comparison with Eulerian-Eulerian methods like TFM, these models can predict the hydrodynamics of fluidized...
Design a Cartesian, Decoupled and Isotropic 5-DoF Parallel Manipulator
, M.Sc. Thesis Sharif University of Technology ; Zohoor, Hassan (Supervisor)
Abstract
Given the optimum design importance of parallel mechanisms, characteristics such as degree of freedom, decoupled and isotropic in structural synthesis of these mechanisms are considered. Also, due to less attention to the development of 5-DoF parallel manipulators, in this research, the improvement of this types of mechanisms is considered. In this research effort to design 5-DoF cartesian, decoupled and isotropic parallel manipulators leads to represent four numbers of this type of mechanisms with 3T2R and 2T3R degrees of freedom. Represented PMs verified with linear transformation theory. Morever by using Jacobian, they more analyzed for their decoupled and isotropic specifications in...
Study on The Influence of Nanoparticles and Magnetic Field on The Liquid-Liquid Mass Transfer Coefficients
,
M.Sc. Thesis
Sharif University of Technology
;
Molaei Dehkordi, Asghar
(Supervisor)
Abstract
Magnetite (Fe3O4) nanoparticles were synthesized and coated with Oleic Acid using the co-precipitation method. The particles were characterized using DLS, FT-IR, SEM, XRD, VSM and UV-Vis spectrophotometry analysis. The mean size of particles was 28.8 nm and the FT-IR analysis indicated that Oleic Acid was coated suitably on the nanoparticles. The vsm test indicated no hysteresis loop for the particles, defining the superparamagnetism of them. A nanofluid containing nanoparticles in 5wt% Acetic Acid in Toluene as the base fliud was prepared. The stability of this nanofluid was determined using UV-Vis spectrophotometry to be less more then 95% in the first two hours. This nanofluid is used as...
Study on the Influence of Nanoparticle and Magnetic Field on Flow in Porous Media
,
M.Sc. Thesis
Sharif University of Technology
;
Molaei Dehkordi, Asghar
(Supervisor)
Abstract
In this thesis, the momentum and heat transfer of a ferrofluid in a partially filled vertical porous channel under the influence of nonuniform magnetic field has been investigated. In this magneto-thermo-echanical problem, our objective was to enhance the heat transfer which is attributable to both ferrofluid and porous medium unique characteristics. Accordingly, this problem is twofold and their relevant aspects would be discussed respectively. The ferrofluid flows upward, in the channel and a gradient magnetic field is generated by a permanent magnet in the vicinity of the channel. To solve the system of govering equations,COMSOL Multiphysics software has been used. The results shows that...
Modeling and Simulation of Magnetic Nanofluids Convective Heat Transfer around a Sphere in the Presence of External Magnetic Feild
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
The good performance in cooling, especially in systems with small dimensions, is one of the critical needs of many industries. Heat transfer around sphere in all systems that contain particles, is important. Many methods have been proposed to improve the heat transfer rate but using nanofluids is one of the ways that has attracted more attention than others. Ferrofluids have magnetic properties in addition to nanofluids properties and this has a significant impact in increasing the heat transfer rate. Controlling heat transfer by magnetic field is one of the unique characteristics of this fluid. The project aim is to investigate the effect of magnetic field on heat transfer around sphere in...
Effects of using altered coarse grids on the implementation and computational cost of the multiscale finite volume method
, Article Advances in Water Resources ; Volume 59 , September , 2013 , Pages 221-237 ; 03091708 (ISSN) ; Manzari, M. T ; Sharif University of Technology
2013
Abstract
In the present work, the multiscale finite volume (MsFV) method is implemented on a new coarse grids arrangement. Like grids used in the MsFV methods, the new grid arrangement consists of both coarse and dual coarse grids but here each coarse block in the MsFV method is a dual coarse block and vice versa. Due to using the altered coarse grids, implementation, computational cost, and the reconstruction step differ from the original version of MsFV method. Two reconstruction procedures are proposed and their performances are compared with each other. For a wide range of 2-D and 3-D problem sizes and coarsening ratios, the computational costs of the MsFV methods are investigated. Furthermore, a...
Solid Mixing in Gas-solid Fluidized Bed with an Inlet Jet
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
Because of unique features and numerous advantages, the fluidized bed has been considered as one of the most widely used process equipment in various industries. However, many aspects of the hydrodynamic behavior of the equipment are unknown. In this study, using simulation tool, hydrodynamic behavior and mixing process of binary solids particle mixture in the tapered fluidized bed with a jet at the entrance were studied. Eulerian – Eulerian multifluid model incorporating the kinetic theory of granular flow is used to simulate the gas-solid multiphase flow with open-source MFIX software. To increase the accuracy of the results standard k-ε turbulence model was used. Validation of results was...
A multi-resolution multiscale finite volume method for simulation of fluid flows in heterogeneous porous media
, Article Journal of Computational Physics ; Volume 248 , September , 2013 , Pages 339-362 ; 00219991 (ISSN) ; Taghizadeh Manzari, M ; Sharif University of Technology
2013
Abstract
This paper presents an extension of the multiscale finite volume (MsFV) method to multi-resolution coarse grid solvers for single phase incompressible flows. To achieve this, a grid one level coarser than the coarse grids used in the MsFV method is constructed and the local problems are redefined to compute the basis and correction functions associated with this new grid. To construct the coarse-scale pressure equations, the coarse-scale transmissibility coefficients are calculated using a new multi-point flux approximation (MPFA) method. The estimated coarse-scale pressures are utilized to compute the multiscale pressure solution. Finally a reconstruction step is performed to produce a...
Modeling and Simulation Study of Ammonia Decomposition in Assisted-Membrane Fluidized Bed Reactors
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
Increasing need for energy, non-renewable fossil resources and environmental pollution persuaded investigators to offer hydrogen as a clean alternative fuel. One of efficient methods for producing hydrogen is the ammonia catalytic cracking reaction. The present work the most to caused on the simulation of both 1D and 2D in an assisted-membrane tapered fluidized bed reactor. In 1D simulation several tubes of membrane placed inside the reactor, but in the case of 2D simulation two membrane tubes on the reactor walls were used. In 1D and 2D simulations the compartmental and Eulerian-Eulerian approach were used, respectively. The simulation results indicate that in a constant static bed height,...