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Numerical Simulation and Optimization of Sea Water Desalination by Reverse Osmosis Membrane
, M.Sc. Thesis Sharif University of Technology ; Mousavi, Ali (Supervisor)
Abstract
Reverse osmosis (RO) is by far the most widely used membrane desalination process worldwide. The RO process depends on the properties of semi-permeable membranes which allow the separation of water from a salt solution by applying external pressure higher than the osmotic pressure on the seawater. The main problem in membrane separation process is the fouling of the membrane walls, which decreases the permeate flux. Having spacer filaments in the feed channel has been proven to dynamically change the concentration boundary layer and preventing fouling. The impact of spacer configurations (cavity, zigzag and submerged) on the alleviation of concentration polarization and the enhancement of...
Effects of Nano Metallic Catalysts on The Life-Time and Efficiency of Proton Exchange Membrane Fuel Cells
, M.Sc. Thesis Sharif University of Technology ; Vesaghi, Mohammad Ali (Supervisor)
Abstract
The Fuel cell is an energy converter which converts the chemical energy of a chemical reaction to electricity and heat directly and without any pollution. One of the most important types of fuel cells is the proton exchange membrane (PEM) fuel cell. The importance of PEM fuel cells is a result of their high energy density, quick start up ability, lower operating temperature, high efficiency and low or zero emissions. Catalysts play an important role in both costs and durability of PEM fuel cells. Alloying the Pt with other metals can increase the activity of the catalysts of the fuel cells and also reduces the amount of costly Pt. In this study, the nanoparticles of Ni were added to the...
Optimal Design of the Heliostat Field in the Solar Central Receiver Systems
, M.Sc. Thesis Sharif University of Technology ; Boroushaki, Mehrdad (Supervisor)
Abstract
In a solar central system plant about 40% of energy losses occurs in the heliostat field. Furtheremore, half of the investment costs for construction of the plant is related to the heliostat field. Therefore, an optimal design of the heliostat field is necessary for reduction of levelized cost of energy in solar tower power plants. In this study, in order to optimally design the heliostat field, first energy performance of the helistat field in one year is simulated. Solar power and sun’s position at each moment of the day is determined by mathematical relations. Then, loss factors in the field are modelled and heliostat field layout is designed by an algorithm. Finally, by using PSO...
A Two-dimensional Modeling and Numerical Simulation of PEM Fuel Cell
, M.Sc. Thesis Sharif University of Technology ; Taghizadeh Manzari, Mehrdad (Supervisor) ; Roshandel, Ramin (Supervisor)
Abstract
In this research, a simple yet efficient two-dimensional model of proton exchange membrane fuel cell (PEMFC) is developed using stream function-vorticity formulation. The model accounts for the fluid flow and masstransport processes in cathode gas channel and gas diffuser layer. The governing equations are decoupled and solved usingtwo efficient approaches, Alternating Direction Implicit (ADI) and False Transient Method (FTM) in a modified geometry to simulate the fully-developed condition consistently. An in-house code was developed to perform a parametric study of fuel cell performance. The results show the variations of important parameters along the cathode channel such as velocity...
Investigation and Modeling of Polymer Electrolyte Membranes in PEM Fuel Cells
, M.Sc. Thesis Sharif University of Technology ; Roshandel, Ramin (Supervisor)
Abstract
Fuel cells convert the chemical energy of hydrogen and oxygen directly into the electricity. Their high efficiency and low emissions have made them a prime candidate for powering the next generation electric vehicles. Polymer electrolyte membrane is a key component of the PEM fuel cells. One of the critical problems to overcome in some PEM fuel cells is the water management because If there is not enough water, the membrane becomes dehydrated which leads to a rapid increase in ohmic resistance. On the other hand, if too much water is present, flooding may occur resulting in the pores of the gas diffusion filled by water and the available passage for reactant gases is decreased. In this work...
Investigation the Effect of Different Pattern of Bi-Polar Plates on PEM Fuel Cells Performance
, M.Sc. Thesis Sharif University of Technology ; Roshandel, Ramin (Supervisor) ; Saboohi, Yadollah (Supervisor)
Abstract
Proton exchange membrane (PEM) fuel cell performance is directly related to the flow channel design on bipolar plates. Power gains can be found by varying the type, size, or arrangement of channels. It has been understood that the flow field design has a deterministic role on mass transport and water management, and thus great efforts have been made for the optimal design of flow field such that high and stable cell performance can be achieved. This study concentrates on the improvement in the performance of PEM fuel cells through optimization of the channel dimensions and patterns in the velocity and pressure fields in bipolar plates. For design and optimization purposes, a 2D numerical...
Three Dimensional Computational Modeling of Multiphase Flow in Proton Exchange Membrane Fuel Cells
, M.Sc. Thesis Sharif University of Technology ; Mazaheri, Karim (Supervisor) ; Roshandel, Ramin (Supervisor)
Abstract
Proton exchange membrane (PEM) fuel cell performance is directly related to the flow channel design on bipolar plates. Power gains can be found by varying the type, size, or arrangement of channels. It has been understood that the flow field design has deterministic role on mass transport and water management in a PEM Fuel cell. This study concentrates on improvements in the fuel cell performance through optimization of channel dimensions and configurations. A 3D, multi-component numerical model of flow distribution based on the Navier-Stokes equations using individual computer code is presented. The simulation results showed excellent agreement with the experimental results in previous...
Numerical Modeling of Terrestrial Planet Temperature Distribution Effect on Polar Vortex Forming: Venus Modeling
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
A global rotating atmosphere with polar vortex and super rotation is simulated using a simplified Venus General Circulation Model (GCM). The polar vortex is maintained strongly by meridional circulation develops in the form of a simple Hadley cell, extending from the equator to the pole in both hemispheres and rotation terrestrial planet. Venus Total Polar Vortex Parameter (PVP) was defined like globally integrated super-rotation but at polar skullcaps (60-90 deg). Venus Polar Vortex Parameter is PVP=1.5 that’s qualitatively similar to observed polar vortex. Then with study in terrestrial planet and Titan modeling, we appointed the Polar Vortex Parameter and critical limit of Polar Vortex...
Predicting the Polarity of Electronic Word-of-Mouth Communication Created on Tweets Messages Posted by Health Policy Makers Related to Covid-19
, M.Sc. Thesis Sharif University of Technology ; Aslani, Shirin (Supervisor)
Abstract
Health influencers leveraged social networks to connect with people and society during the Covid-19 crisis. Platforms like Twitter served as suitable channels for disseminating published messages through word-of-mouth communication. In times of crises like Covid-19, individuals and organizations involved in managing the situation harnessed this capability, contingent upon the quantity and quality of word-of-mouth exchanges. During public crises, public polarity and sentiment toward the issue and the maintenance of public morale hold paramount significance. Consequently, crafting messages that garner positive word-of-mouth communication became a focal point for health influencers. In this...
Using Numerical Simulation in the Design and Analysis of Spiral PEM Fuel Cells
, M.Sc. Thesis Sharif University of Technology ; Kazem Zadeh Hannani, Siamak (Supervisor) ; Taghizadeh Manzari, Mehrdad (Supervisor) ; Roshandel, Ramin (Co-Advisor)
Abstract
The gas flow field geometry influences the transport phenomena inside PEMFCs and hence affecting their overall performance. Radial force and secondary flows resulting from curvature of the spiral channels in PEMFCs can improve mass transport limits and so does to their overall performance. Studying the effects of curvature of spiral channels on fuel cell performance and comparing them with similar designs is the aim of this thesis. The geometries are generated using concentric Archimedes’ spirals and categorized as axial or radial depending on the direction of the vector perpendicular to their MEA . Each category has five geometries which are the result of branching the main channel into...
Corrosion Behavior of TLP Bonded 304 Stainless Steel Using Cobalt Base Interlayer
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor) ; Tavakoli, Rouhollah (Supervisor)
Abstract
The transient liquid phase bonding is a combination of penetration bonding and hard soldering processes. This method is based on the diffusion in the solid state of the melting point reducing elements from the joint zone into the base metal and isothermal solidification that the kinetics of this reaction are controlled by diffusion in the solid state. In this study, we investigate the bonding of 304 stainless steel with cobalt base interlayer by transient liquid phase method and studies of microstructural and corrosion resistance of the joint. Three different temperatures are considered for the bonding and after each bonding, the microstructure is examined with a optical and scanning...
Super Hydrophobic Ni Coating on Steel by Electrodeposition Method
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
In this study, the properties of super-hydrophobic Ni coating on carbon steel including wetting behavior and corrosion resistance of Nickel coatings deposited on the steel substrate were investigated. For this purpose, Nickel coatings deposited by electrodeposition method in deferent current density (10,20,30,50, 70 mA /cm2) in bath containing 1.5 mol of ethylene de-ammonium de-chloride, 0.5 mol H3BO3, 1 mol Nicl2.6H2o and then immersed in a bath containing 0.01 mol per liter myristic acid and ethanol for 24 hours and then placed in the room temperature for 14 days. Deferent tests were used for characterization, wettability properties, corrosion behavior and morphology of Ni coatings. The...
An Investigation into the Microstructure and Mechanical Properties of Biodegradable Magnesium Alloys Composite-carbon Nanotube Produced by the Mechanical Alloying and Powders Pressing Processes
, M.Sc. Thesis Sharif University of Technology ; Karimi Taheri, Ali (Supervisor)
Abstract
Properties of biomaterials, especially in application as planting, can be controlled and optimized by alloying and hardening sedimentation. In recent years, the study on the simultaneous improvement of mechanical properties, toughness and corrosion behavior of magnesium composite by carbon nanotubes (CNTs) is very limited. In this study, the behavior of mechanical properties and corrosion of magnesium alloy composites with different percentages of CNTs have been investigated. The production of magnesium alloy composite by powder metallurgy and aging process have been used as effective methods for improving mechanical properties and increasing the corrosion resistance of magnesium alloys. For...
Survey of Corrosion and Biocompatibility of Metallic Biomaterials in Simulated Body Fluids
, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdollah (Supervisor)
Abstract
In this project, the aim is finding the corrosion behavior and biocompatibility of metallic biomaterials in simulated body fluids.by this study we can have a wide knowledge about the behavior and use of metallic biomaterials.in this project we use three base metals. Ti (grade 5 and grade 2), stainless steel (316L and 316) and Mg alloy(AZ91 and AZ31). the media was six physiological environment( Cigada solution, Hank solution, SBF solution, Fusayama solution, Ringer solution and Tyrod’s solution). all of these environments are related to the body fluids except Fusayama solution that is an artificial saliva and is a mouth fluid. we used polarization tests to determine the corrosion behavior...
Formation and Investigation of Zinc-Nickel Two Cathionic Electrophospahte Coating Properties on Galvanized Steel
, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdollah (Supervisor)
Abstract
By using electrophoaphating treatment in the metal coating process, the operating temperature of chemical phosphating bath is decrease and also difficulties with the use of high temperature bath is eliminated. The aim of this study is investigate the effect of operating parameter on coating properties and also investigation the deposition mechanism of Zn-Ni electrophosphate coating. Coating properties such as morphology, corrosion resistance and porosity of the coating characterized using SEM, polarization test and electrochemical method respectively. The values used for pH effect was 1.6,1.8,2 and 2.2 results indicated that by increasing the pH value from 1.6 to 1.8 the icorr decrease from...
Design and Manufacture of Nanostructured Hydroxyapatite coated Foamy core@compact Shell Ti-6Al-4V Nanocomposite
, M.Sc. Thesis Sharif University of Technology ; Sadrnezhad, Khatiboleslam (Supervisor)
Abstract
The main purpose of this research is design and manufacture of nanostructured hydroxyapatite-coated foamy core@compact shell Ti-6Al-4V bone-like composites for utilization as substitutive implant for cortical bone having porous core. The production procedure consist of two steps; (a) fabrication of foamy core@compact shell Ti-6Al-4V alloy using powder metallurgy-space holder technique, (b) precipitation of hydroxyapatite on the Ti-6Al-4V alloy specimens via pulse electrodeposition process. The bone-like structures were designed to reduce the stress shielding which ensures long-term stabilization of implants. It is while that, the hydroxyapatite coating improve the biological response of...
Study the Effect of Specific Salt Ions on Interfacial Tension of Water (Lowsalinity/Smart) and Reservoir Fluid in Surface Tension Reducing Materials Flooding by Molecular Dynamic Simulation
, M.Sc. Thesis Sharif University of Technology ; Ayatollahi, Shahabodin (Supervisor)
Abstract
Water injection is known as one of the most efficient and affordable techniques to displace the oil in the reservoirs. To increase oil recovery efficiency through water injection operation, recently low salinity water injection or water containing a certain amount of effective ions (engineered/low salinity water) is proposed. Besides, improving this technique is also adopted in the oil industry using certain chemicals like surfactants to change the interfacial tension or rock wettability for more oil recovery. In order to study and model the mechanisms involved during surfactant flooding, molecular dynamics simulation is utilized here as a novel technique. The advantage of this method over...
Improve the Rheological Behavior of Different Waxy Crude Oil by Using Variouse Additives
, M.Sc. Thesis Sharif University of Technology ; Ghotbi, Cyrus (Supervisor) ; Jafari Behbahani, Taraneh (Supervisor) ; Ramezani Saadatabadi, Ahmad (Co-Supervisor)
Abstract
Wax precipitation is one of the major problems in the transfer of crude oil from field production to refineries. This wax with asphaltene compounds and some water and solids, closes the oil pipeline. One of the ways to reduce the amount of wax in pipes is to use additives (flow improvers) to crude oil and improve its rheological behavior. In this research, Five Iranian crude oils were characterized with SARA test and then the effects of various additives including ethylene vinyl acetate (EVA) in concentrations of 500 and 1500 ppm, alkyl phenol ormaldehyde resins (NPFR) with 1500 ppm and styrene-(ethylene-cobutylene)- styrene (SEBS) with 1500 ppm on viscosity, wax appearance temperature...
Modified Forward Osmosis Membrane Preparation for Portable Water Purification Systems
, M.Sc. Thesis Sharif University of Technology ; Mousavi, Abbas (Supervisor) ; Ramazani Saadat Abadi, Ahmad (Supervisor)
Abstract
In this study, mesh-reinforced cellulose acetate (CA)-based membranes were prepared for forward osmosis (FO) by immersion precipitation. Casting composition, preparation conditions, evaporation time, coagulation bath temperature, annealing temperature, CA percent and 1,4-dioxane/acetone ratio were tested for membranes’ performance. Also, the results were compared with commercially CTA membranes. The FO membrane prepared under optimized conditions had a smooth surface similar to commercial ones. The most proper membrane (17.9 % polymer and 1,4-dioxane /acetone ratio 1.89) showed water flux of 9.3 L/m2.hr (LMH) and RSF of 0.536 mol NaCl/m2.hr. Using mesh in the membrane structure, different...
Modeling and Simulation of Bioelectrochemical Systems
, M.Sc. Thesis Sharif University of Technology ; Yaghmaei, Soheyla (Supervisor)
Abstract
The objective of the present research, for the first time, was to configure a novel dynamic model to be applied in a general manner to simulate bioelectrochemical systems including microbial fuel cell and microbial electrolysis cell. Biochemical reactions engaged in organic substances degradation in both anolyte and biofilm were described by two anaerobic digestion models; Bernard’s anaerobic digestion model and ADM1. In addition, the bioelectrogenesis and electron transfer were modeled based on the direct electron transfer mechanism across the conductive biofilm. The biofilm simulation was established upon the one-dimensional distributions of substrates and microorganisms. In this study,...