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Investigation of mass transfer coefficient under jetting conditions in a liquid-liquid extraction system
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 29, Issue 1 , 2010 , Pages 1-12 ; 10219986 (ISSN) ; Omidkhah, M. R ; Bastani, D ; Saifkordi, A. A ; Sharif University of Technology
Abstract
In this research mass transfer coefficient under jetting regime in different directions (from dispersed to continuous and continuous to dispersed phase) has been studied using an experimental setup. n-Butanol-succinic acid-water with low interfacial tension has been selected as experimental chemical system. The effects of various parameters such as jet velocity, nozzle diameter and the height of the continuous phase above the nozzle, on mass transfer coefficient have been investigated. A correlation has also been derived in order to predict the mass transfer coefficient as a function of physical properties of both phases and aforementioned parameters. Based on the experimental results, mass...
Modeling of Water Injection into the Desuperheater of Steam Generator
, M.Sc. Thesis Sharif University of Technology ; Saidi, Mohammad Hasan (Supervisor)
Abstract
One of the most important equipment in a power station is desuperheater which its operation has effect on power station performance and efficiency.It is necessary to identify and evaluate the most important factors that have effect on its performance. Using desuperheater cause that the temperature of exhausting superheat steam of boiler decreases to the desired quantity. If the temperature of superheat steam is very high, it will cause burning of superheater pipes that is very dangerous.Steam is used for two purpose of power generating and operational process. Unfortunately these applications have different requirement. In power generating for maximizing efficiency, turbine needs high...
Electrowetting induced droplet generation in T-junctions
, Article Journal of Heat Transfer ; Volume 143, Issue 5 , 2021 ; 00221481 (ISSN) ; Moosavi, A ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2021
Abstract
In this study, droplet generation in a T-junction fluidic channel device was studied by using electrowetting actuation with the consideration of different droplet forming regimes. For this purpose, the finite element method (FEM) was used to solve the unsteady Naiver-Stokes equation. In addition, the level set method was applied to capture the interface between two phases. It was shown that there was a good agreement between obtained data and other work during the process of droplet generation in the absence of electrowetting actuation which results in the decrease in the size of the droplet with increasing the velocity ratios. In the shearing regime, the effectiveness of electrowetting on...
Recovery of Uranium from the Waste of UCF Plant By Means of Solvent Extraction Method
, M.Sc. Thesis Sharif University of Technology ; Samadfam, Mohammad (Supervisor) ; Taghizadeh, Mohammad (Supervisor)
Abstract
During various stages of processing uranium in Isfahan’s UCF plant, liquid waste containing uranium compounds, is directed to evaporation lagoons. Gradually, a considerable amount of precipitation will form at the bottom of the lagoons. Since the concentration of uranium in evaporation ponds is relatively high, it seems that in addition to environmental issues, recycling uranium from existing pools is also economical. Uranium may be recovered from an aqueous solution by precipitation, solvent extraction and ion exchange. The solvent extraction is the best option for our purpose because of simple operation without increased consumption of heat or chemicals. It is also preferable when large...
Dispersed phase holdup in a pulsed disc and doughnut extraction column
, Article Brazilian Journal of Chemical Engineering ; Volume 28, Issue 2 , June , 2011 , Pages 313-323 ; 01046632 (ISSN) ; Jalilvand, H ; Outokesh, M ; Sharif University of Technology
2011
Abstract
Dispersed phase holdup has been measured in a 76 mm diameter pulsed disc and doughnut extraction column for three different liquid-liquid systems. The effects of operational variables such as pulsation intensity and dispersed and continuous phase flow rates on holdup have been investigated and found to be significant. The existence of three different operational regimes, namely mixer-settler, dispersion, and emulsion regimes, was observed when the energy input was changed. The results indicated that the characteristic velocity approach is applicable to this type of extraction column for analysis of holdup in the transition and emulsion regions. Empirical correlations are derived for...
Mass transfer coefficients of extracting Mo (VI) and W (VI) in a stirred tank by solvent extraction using mixture of Cyanex272 and D2EHPA
, Article Separation Science and Technology (Philadelphia) ; 2019 ; 01496395 (ISSN) ; Torab Mostaedi, M ; Outokesh, M ; Asadollahzadeh, M ; Sharif University of Technology
Taylor and Francis Inc
2019
Abstract
In this study, the mass transfer evaluation of an agitated liquid-liquid system for the extraction of molybdenum and tungsten from aqueous sulfate solution was investigated. It was found from batch experiments for separation of molybdenum from tungsten that the initial aqueous pH, Cyanex272 and D2EHPA concentration, contact time, dispersed phase volume fraction and impeller speed were optimized at 1.3, 0.07 M, 0.29 M, 15 min, 0.09 and 280 rpm, respectively. The results indicate that a suitable composition for stripping is 1.5 M NH4OH and 0.6 M NH4F. Furthermore, a modified correlation based on dimensionless numbers was derived for the prediction of continuous phase mass transfer in the...
Controlling the microscale separation of immiscible liquids using geometry: A computational fluid dynamics study
, Article Chemical Engineering Science ; Volume 220 , 2020 ; Mohammadi, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this study, we numerically determined the performance of a microscale separator comprising a lateral and a main channel to separate a two-phase flow. It was aimed to conduct continuous phase through the lateral channel and dispersed phase through the main channel. The continuous and dispersed phases were modeled as incompressible Newtonian fluids with the corresponding interface tracked by the phase-field model. The dynamics, including pressure fluctuations in the separator, were further examined. It was mechanistically demonstrated how the geometry of the separator modulates the phase separation. Further examined were the influences of various geometrical parameters on the performance of...
Mass transfer coefficients of extracting Mo (VI) and W (VI) in a stirred tank by solvent extraction using mixture of Cyanex272 and D2EHPA
, Article Separation Science and Technology (Philadelphia) ; Volume 55, Issue 17 , 2020 , Pages 3140-3150 ; Torab Mostaedi, M ; Outokesh, M ; Asadollahzadeh, M ; Sharif University of Technology
Bellwether Publishing, Ltd
2020
Abstract
In this study, the mass transfer evaluation of an agitated liquid-liquid system for the extraction of molybdenum and tungsten from aqueous sulfate solution was investigated. It was found from batch experiments for separation of molybdenum from tungsten that the initial aqueous pH, Cyanex272 and D2EHPA concentration, contact time, dispersed phase volume fraction and impeller speed were optimized at 1.3, 0.07 M, 0.29 M, 15 min, 0.09 and 280 rpm, respectively. The results indicate that a suitable composition for stripping is 1.5 M NH4OH and 0.6 M NH4F. Furthermore, a modified correlation based on dimensionless numbers was derived for the prediction of continuous phase mass transfer in the...
Phase-type Distribution in the Sequencing and Scheduling Problem and its Application in Operating Room Problem
, Ph.D. Dissertation Sharif University of Technology ; Salmasi, Nasser (Supervisor) ; Modarres, Mohammad (Supervisor)
Abstract
Operating rooms (ORs) are considered as the most valuable resource in hospital, which are the largest revenue generator and, at the same time, the largest cost center of hospitals. Hospital managers have been interested in improving the efficiency and effectiveness of ORs by developing modern planning and scheduling tools. This research studies the stochastic operating room (OR) scheduling problem integrated by Post-Anesthesia Care Unit (PACU), named the operating theater room (OTR) problem. Due to the inherent uncertainty in surgery duration and its consecutive PACU time, the completion time of the operation of a patient should be modeled as the sum of a number of random variables. Several...
Effects of Measures on Phase Transitions in Two Cooperative Susceptible Infectious Recovered (SIR) Dynamics
, M.Sc. Thesis Sharif University of Technology ; Ghanbarnejad, Fakhteh (Supervisor)
Abstract
In recent studies, it has been shown that a cooperative interaction in a co-infection spread can lead to a discontinuous transition at a decreased threshold. Here, we have investigated effects of immunization on the threshold and the type of phase transitions in a cooperative spread of two diseases. It has been assumed that the immunization begins at the start of the spread and it is perfect, meaning that the vaccinated are immune for ever. We have used the SIR model for the spread of two diseases and scrutinized phase transitions through a mean field approach. This study is divided into three parts. In the first part, vaccination with a fixed rate has been introduced in the symmetric spread...
Improving Patient Flow in the Emergency Department with Dynamic Scheduling Using Phase-Type Distribution Function
, M.Sc. Thesis Sharif University of Technology ; Varmazyar, Mohsen (Supervisor)
Abstract
The Emergency Department is one of the most important departments in a hospital, which is continuously active and plays a crucial role in saving patients' lives. For this reason, using research methods in operations and optimization can greatly help improve the performance of the Emergency Department. In this thesis, the emergency scheduling problem is examined with the objective function of minimizing the total weighted sum of job completion times, considering the random nature of service times. Since the objective function of the problem is to minimize the total job completion time, the job completion time is obtained as the sum of several random variables. Considering the additivity...
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...
Realization of constant envelope OFDM using quantization and CPM technique
, Article AEU - International Journal of Electronics and Communications ; Volume 80 , 2017 , Pages 172-178 ; 14348411 (ISSN) ; Mohammadi, A ; Afrashteh, N ; Sanjaroonpouri, V ; Sharif University of Technology
Abstract
Orthogonal frequency division multiplexing (OFDM) is used in many wireless communication. The important drawback of this modulation is its high peak-to-average power ratio (PAPR). In this paper, a new modulation scheme of constant-envelope OFDM (CE-OFDM) is proposed. This scheme uses a combination of OFDM, quantizer and continuous phase modulation (CPM) to achieves 0 dB PAPR. The statistical signatures of signals, based on system parameters such as the length of discrete Fourier transform (DFT) and the number of quantization levels are presented. There are two sources of noise in proposed CE-OFDM scheme: quantization noise and channel noise. The theoretical analysis of these noises is...
Effect of poly (propylene-g-maleic anhydride) on the morphological, rheological, and mechanical properties of PP/HDPE blend
, Article Journal of Thermoplastic Composite Materials ; Volume 22, Issue 5 , 2009 , Pages 519-530 ; 08927057 (ISSN) ; Abdi Valami, M ; Khak, M ; Sharif University of Technology
2009
Abstract
In this study, the morphological, rheological, and mechanical properties of PP/HDPE blend compatibilized with poly (propylene-g-maleic anhydride) were studied. Necessary blends were prepared using a counter current twin-screw extruder. The blend composition ranged from 10 to 50 wt% of dispersed phase (HDPE) and compatibilizer (MAPP) with two Concentration ranges 10, 20 wt% were used for PP/HDPE (80/20) blend with respect to the dispersed phase (HDPE). The results of morphological studies shows a droplet dispersion morphology in the composition to 50wt% HDPE content, which indicates that HDPE forms a dispersed phase and PP forms a continuous phase in these composition region. Addition of the...
Numerical modeling of splashing and air entrapment in high-pressure die casting
, Article International Journal of Advanced Manufacturing Technology ; Volume 39, Issue 3-4 , 2008 , Pages 219-228 ; 02683768 (ISSN) ; Babaei, R ; Attar, E ; Shahinfar, S ; Davami, P ; Sharif University of Technology
2008
Abstract
High-pressure die casting (HPDC) is one of the most important manufacturing processes. Air porosity in HPDC parts has many serious effects upon the casting quality. A 3D single-phase code based on the SOLA-VOF algorithm is used for the continuous phase advection during mold filling. In this research, a computational model based on concentration transport equation is used for calculation of air porosity distribution and a mixed VOF-Lagrange algorithm is developed in order to model splashing in HPDC. Finally, Schmid's experimental tests are used to verify the modelling results and the comparison between the experimental data and simulation results has shown a good agreement. © 2007...
Analysis of structure-properties relationship in nitrile-butadiene rubber/phenolic resin/organoclay ternary nanocomposites using simple model system
, Article Polymers for Advanced Technologies ; Volume 21, Issue 5 , April , 2010 , Pages 356-364 ; 10427147 (ISSN) ; Faghihi, M ; Sharif University of Technology
2010
Abstract
The present study deals with the structure-property relationship of organoclay (OC) filled nanocomposites based on rubber blend comprising of nitrile-butadiene rubber (NBR) and phenolic resin (PH). To obtain a better insight into the characteristics of the NBR/PH/OC hybrid system, a simple model system consisting of NBR/OC nanocomposites is also taken into consideration. A series of NBR/OC and NBR/PH/OC nanocomposites containing a wide range of OC concentrations (2.5-30 phr) are prepared by using traditional open two-roll mill. Structural analysis performed by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) exhibits mixed exfoliated and...
Three-dimensional simulation of hydrodynamics in a rotating disc contactor using computational fluid dynamics
, Article Chemical Engineering and Technology ; Volume 32, Issue 1 , 2009 , Pages 93-102 ; 09307516 (ISSN) ; Hedayat, N ; Ziyari, A ; Kazemzadeh, M ; Shafiee, M ; Sharif University of Technology
2009
Abstract
The 3D simulation of the hydrodynamic behavior of a rotating disc contactor (RDC) by means of computational fluid dynamics (CFD) was investigated for the n-butanol-succinic acid-water (BSW) system. For the two-phase liquid-liquid flow, the velocity distribution of the continuous phase and drop size distributions were determined using the k-ω turbulence model in conjunction with the Eulerian-Eulerian approach and MUSIG model. In this system in which the holdup of the dispersed phase is low, the continuous phase velocity was computed by simultaneously solving the Navier-Stokes equations beside the different models of turbulence. The motions of the dispersed phase was calculated while...
Numerical simulation of vortex engine flow field: One phase and two phases
, Article Journal of Thermal Science ; Volume 18, Issue 3 , 2009 , Pages 226-234 ; 10032169 (ISSN) ; Saemi, S. D ; Saidi, M. H ; Sharif University of Technology
2009
Abstract
Aiming at improving efficiency in combustion systems, the study on droplet behavior and its trajectory is of crucial importance. Vortex engine is a kind of internal combustion engine which uses swirl flow to achieve higher combustion efficiency. One of the important advantages of designing vortex engine is to reduce the temperature of walls by confining the combustion products in the inner vortex. The scopes of this investigation are to study vortex engine flow field as well as effective parameters on fuel droplet behavior such as droplet diameter, droplet initial velocity and inlet velocity of the flow field. The flow field is simulated using Reynolds Stress Transport Model (RSM). The...
New approach in the prediction of RDC liquid-liquid extraction column parameters
, Article Chemical Engineering and Technology ; Volume 31, Issue 7 , 2008 , Pages 971-977 ; 09307516 (ISSN) ; Shahalami, S. M ; Sharif University of Technology
2008
Abstract
The liquid-liquid extraction process is well-known for its complexity and often entails intensive modeling and computational efforts to simulate its dynamic behavior. This paper presents a new application of the Genetic Algorithm (GA) to predict the modeling parameters of a chemical pilot plant involving a rotating disc liquid-liquid extraction contactor (RDC). In this process, the droplet behavior of the dispersed phase has a strong influence on the mass transfer performance of the column. The mass transfer mechanism inside the drops of the dispersed phase was modeled by the Handlos-Baron circulating drop model with consideration of the effect of forward mixing. Using the Genetic Algorithm...