Loading...
Search for:
afshin--hossein
0.028 seconds
Total 70 records
Experimental Investigation of Surfactant Effects on Drop Formation of Shear-thinning Liquids
, M.Sc. Thesis Sharif University of Technology ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Supervisor)
Abstract
In this research, the characteristics of non-Newtonian, shear-thinning drop formation containing surfactant from a needle are investigated experimentally. The ambient fluid is air and all experiments have been conducted in a constant flow rate of drop phase fluid. Images of forming drop are taken using a high-speed camera and by processing them, important parameters in drop formation such as length of drop, minimum neck thickness, formation time and the size of satellite drops have been studied. Three non-Newtonian and three Newtonian fluids are considered in a way that the initial viscosity of non-Newtonian fluids would be equal to the viscosity of their corresponding Newtonian fluids....
The Study of the Effect of Surfactant on the Liquid Drop Motion In Fluid
, M.Sc. Thesis Sharif University of Technology ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Co-Supervisor)
Abstract
The drop motion in fluid and the mass transfer is one of the most interesting and favorite topics that has attracted the attention of many researchers. Knowing the functions of the factors affecting the deformation and the process of mass transfer and the effects of the addition of the surfactant, improve the efficiency of the related industrial processes.In this regard, the present study examines how the shape and speed of a moving Newtonian drop in a Newtonian fluid, the mass transfer of soluble material from inside the drop to the surrounding fluid and also the study of the effect of surfactant on the dynamics of moving droplet is studied numerically. During the drop movement, the...
Experimental and Theoretical Investigation of Ascending Accelerated Motion of Single Bubble in Quiescent Newtonian and Non-newtonian Liquids
, M.Sc. Thesis Sharif University of Technology ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Supervisor)
Abstract
The gas-liquid interaction is one of the most important and common phenomenons in chemical, biochemical and mineral industries which is generally observed as liquid in a gas stream (droplet) or gas in a liquid stream (bubble). Although bubbles produced in the industrial applications are in the form of a group of bubbles, understanding the hydrodynamics of a single bubble in a quiescent liquid provides a starting point for studying bubble groups. It should be noted that changes in the velocity and drag coefficient of the bubbles in various fluids are essential parameters for designing gas-liquid systems. In the present research, in order to examine the effect of system parameters and...
Experimental Study of a Single Bubble Formation and Its Deformation in Shear-thinning Fluids
, M.Sc. Thesis Sharif University of Technology ; Afshin, Hossein (Supervisor) ; Firoozabadi, Bahar (Supervisor)
Abstract
Bubble formation and bubble rising are widely used in many industrial processes such as bubble columns, extraction, fermentation, foaming and polymerization. Although many of these processes are faced with a series of bubbles, this study may help us better understand the hydrodynamics of single bubble formation and bubble rising and provides a deep insight into the modeling of a series of bubbles. Bubble velocity and drag coefficient in various fluids are the major parameters for designing the liquid-gas systems. These parameters are a function of the bubble size. In this study, single bubble formation is theoretically modelled in order to predict the size of the bubble at the moment of...
Experimental Investigation on the Accelerated Motion of Newtonian and Non-Newtonian Liquid Drops
, M.Sc. Thesis Sharif University of Technology ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Supervisor)
Abstract
Motion of liquid drops into another fluid is of central importance in a variety of most commonly used industries. Vast applications of emulsions in food and drug industries as well as using of drops in liquid-liquid extraction processes and direct contact heat exchangers are examples in which dynamics of motion of drops play a significant role in operation and efficiency.
In present study, we consider the accelerated motion of Newtonian and non-Newtonian liquid drops experimentally. In order to find the effect of bulk fluid on the motion of drops, air and water are used as bulk fluid. The experiments have been done on Water, Ethanol, Ethyl acetate, n-Hexane and Toluene as Newtonian and...
In present study, we consider the accelerated motion of Newtonian and non-Newtonian liquid drops experimentally. In order to find the effect of bulk fluid on the motion of drops, air and water are used as bulk fluid. The experiments have been done on Water, Ethanol, Ethyl acetate, n-Hexane and Toluene as Newtonian and...
Kinetic Analysis of Pyrolysis Modelling of Non-Charring Polymers
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor) ; Afshin, Hossein (Co-Advisor)
Abstract
In this research, modelling of pyrolysis in small-scale and a method for calculation of kinetic parameters; activation energy, pre-exponential factor, and model function, have been presented. Calculation of activation energy and frequency factor without any assumption on model function heve been done by presented method. Because, incorrect assumption on model function can be cause to error in estimated values of activation energy and frequency factor.For a bench-scale sample, the heat transfer and mass conservations equations influence the pyrolysis process. In this research for the investigation of kinetic parameter effects, a simple pyrolysis model was presented to predicting the mass flux...
Numerical Simulation of Spray and Combustion in a Gasoline Direct Injection (GDI) Engine
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Vahid (Supervisor) ; Afshin, Hossein (Supervisor)
Abstract
Energy crisis is one of the crises which human beings face these days. Optimizing the operation of energy consuming machines is one of the most effective methods in decreasing energy consumption. Gasoline direct injection engines as new achievements in automobile and propulsion industry, reduce fuel consumption by increasing the engine efficiency. In these types of engines, a high pressure injector injects fuel directly into the combustion chamber instead of injecting fuel in intake ports. Thus, because of evaporation cooling, the mixture cools down, so the possibility of achieving higher compression ratios in higher engine speeds and loads, without occurrence of knock is provided. Increase...
Design and Performance Analysis of a Reversible Axial Flow Fan and Study of Symmetric Profile Effects
, M.Sc. Thesis Sharif University of Technology ; Afshin, Hossein (Supervisor) ; Farhanieh, Bijan (Co-Advisor)
Abstract
Smoke must be exhausted, as the first action, in probable fire in subways, underground transportation systems and mines in order to survive people exposed to it. To achieving this purpose, the axial fan should be used to move the smoke to the exit lines. These fans should be had same performances in suction and discharge directions (main and reverse directions). This means flow rate should be the same at main and reverse directions. Therefore, fully reversible axial flow fans should be used in emergency ventilations. The fully reversible axial flow fans have same efficiencies in suction and discharge directions. The symmetric profiles should be used in manufacturing of the blades of these...
Simulation of Mass Transfer from Droplet in a Two Phase Liquid-liquid Extraction System
, M.Sc. Thesis Sharif University of Technology ; Afshin, Hossein (Supervisor) ; Firoozabadi, Bahar (Co-Advisor)
Abstract
Mass transfer of a drop moving in a bulk fluid is an interesting subject which has attracted a lot of attention. Understanding effective parameters in this process would be helpful in order to increase the efficiency of the industrial processes related to mass transfer. In this research, the deformation and mas transfer of a moving drop was studied numerically. Navier-Stokes equations and concentration equation were solved separately with a VOF method in an axisymmetric domain using Fluent software. Comparision between numerical results and former experimental results proves the accuracy of the modelling in both fields of deformation and mass transfer. Moreover, effects of the physical...
Numerical Study of Gas Release, Diffusion and Explosion in the High Pressure Gas Pipeline
, Ph.D. Dissertation Sharif University of Technology ; Farhanieh, Bijan (Supervisor) ; Afshin, Hossein (Co-Supervisor)
Abstract
With the advent and development of modern technologies, the need for energy in industrial societies has been dramatically increased. Currently, natural gas is considered as one of the most important energy sources in the world. High pressure transmission lines are widely used to transfer natural gas from wells and natural resources to industrial centers. High costs, limited results, and the potential risks of empirical experiments along with further need for problem simplification in analytical studies have led numerical methods to become the most practical tools for researchers in the safety field of high pressure gas transmission lines. Numerical simulations of explosive events require a...
Design, Simulation, Performance Analysis, Optimization, Fabrication and Experimental Test of a Large Scale Reversible Axial Flow Fan
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor) ; Afshin, Hossein (Co-Advisor)
Abstract
During fires, smoke particles are emitted in the air and the oxygen content of it rapidly drops. In order to tackle these two challenges which are among the main human life threatening factors, there is a need for a proper ventilation system. Ventilation is also one of the most sensitive and vital technical aspects in construction of tunnels and mines. Ventilation fans are tasked with two main objectives which are diluting the air inside the tunnel, parking, etc. and the timely discharge of smoke in case of fire. Hence, they should have similar operation in suctioning and discharge and supply the required flow rate in both directions. This is the reason the fans are reversible. Reversible...
Experimental Study of Droplet Formation in Surfactant Solution
, M.Sc. Thesis Sharif University of Technology ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Co-Advisor)
Abstract
Surfactants are materials that reduces surface tension, and this property has provided a wide range of applications for them. Most of the surfactants reduce surface tensions at the interface of two fluids. The pharmaceutical and food industries, detergents, cosmetics, agricultural pesticides, dye production and oil extraction are among these applications.In this study, the formation of droplets in the presence of three types of surfactants SDS, CTAB and Tween 20 has been investigated. To evaluate the droplet behavior in the presence of specific surfactants, various parameters such as formation time of the droplet, the diameter and length of the droplet formed, the diameter and length of the...
Numerical Investigation of the Effects of Environmental Parameters on the Simulation of Spread of Fire in Grasslands
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor) ; Afshin, Hossein (Co-Supervisor)
Abstract
Fire in Grasslands is one of the most dangerous natural disasters that is uncontrollable at the time of its occurrence and will continue until there is a fundamental change in the conditions of the fire. Fire in Grasslands due to the high density of vegetation can produce a large amount of heat energy in a short time and in a very large area, which alone can cause the spread of fire in Grasslands. Today, numerical studies of fire behaviour and propagation are given more attention than experimental studies due to their lower costs and limitations. In the present study, the numerical simulation of the fire spread with the influence of climate parameters such as humidity, rainfall during fire...
Investigation of Water Mist Performance on Firefighting in Underground Parking Lots
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor) ; Afshin, Hossein (Supervisor)
Abstract
Fire is an undesirable phenomenon that causes human and financial losses. This in itself is a dangerous event that becomes even more dangerous in closed spaces. Car fires in underground car parks are no exception. In this research, the fire caused by burning flammable materials inside the car cabin located in a closed underground parking environment and the performance of sprinkler and water mist nozzles in controlling and extinguishing it have been investigated. Based on the broad foundations of various phenomena affecting this problem, including the separation of solid fuels under the influence of heat and oxygen, chemical reactions, radiant heat transfer and change of liquid phase to...
Numerical Investigation of Different Ventilation Systems in Coal Mines Effects on the Fire Extinguishing
, M.Sc. Thesis Sharif University of Technology ; Afshin, Hossein (Supervisor) ; Farhanieh, Bijan (Co-Supervisor)
Abstract
In recent years, due to fires in mines around the world, the need to study the dynamic behavior of fire to understand how it spreads and design an appropriate fire extinguishing system to reduce damage to people and underground facilities has been felt. Mine fires are usually caused by external sources such as cable connections, methane gas explosions, or coal self-ignition due to oxygen uptake and rising temperatures.In this research, using Fire Dynamic Simulator (FDS) software, after drawing the geometry of a coal tunnel corridor in progress and creating a fire model through pyrolysis of PVC, fire extinguishing was performed by nozzles. If the nozzle does not succeed in extinguishing the...
Design and Optimization of Helium Recovery Process from Natural Gas
, M.Sc. Thesis Sharif University of Technology ; Afshin, Hossein (Supervisor) ; Farhanieh, Bijan (Co-Supervisor)
Abstract
Helium is a valuable substance that is widely used in industry and medicine because of its unique properties. Due to the increasing demand for helium in the global market, several helium extraction units have been launched in the world in recent years; Nevertheless, there is still a significant gap between projected global helium production capacity and demand. Today, natural gas is known as the main source of helium on the earth. The method of industrial extraction of helium from natural gas is cryogenic. Due to the low temperature of this process, relatively high power consumption is used to extract helium from natural gas. Therefore, the optimization of this process is of great...
Numerical and Experimental Study of the Effects of Surfactant on Droplet Motion and Deformation
, Ph.D. Dissertation Sharif University of Technology ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Supervisor)
Abstract
Surface Active Agents/surfactant have a strong tendency to adsorb at the interface between two immiscible fluids, due to the existence of hydrophobic portions in their molecules’ structure. Accumulation of these molecules on the liquid interface changes the intermolecular forces and causes the interfacial tension to decrease. Production of drops of the same size at a specified rate and controlling their movement’s speed are among the most important factors effective in the efficiency of processes associated with liquid drops, which could profoundly be influenced by the presence of a small amount of a surface active agent. In this study, the effects of surface active agents on the growth,...
Investigation of the Fire-Induced Smoke Flow in the Complex Geometries Using The 3d Numerical Method and the Body-Fitted Curvilinear Coordinates
, Ph.D. Dissertation Sharif University of Technology ; Farhanieh, Bijan (Supervisor) ; Afshin, Hossein (Co-Supervisor)
Abstract
With the process of achieving a higher state of social development and technological advances, the need for higher and more strict safety standards has been increased. In this regard, it is of great importance to have an accurate understanding of the fire phenomena and its consequences. Among the adverse effects of fire, a significant percentage of the fire fatalities is related to the fire-induced buoyant gases (smoke) flow which can lead to suffocation. Therefore, it is necessary to know the physics of the fire phenomena well. In fire investigation methods, the numerical study is an appropriate choice, because of the lower executive cost (relative to the experimental study) and the wider...
Development and Assessment of a Numerical Model for Investigation of Regional Dust Distribution
, Ph.D. Dissertation Sharif University of Technology ; Afshin, Hossein (Supervisor) ; Firoozabadi, Bahar (Co-Supervisor)
Abstract
In recent years, dust storms have been recognized as one of the most crucial problems for people worldwide. Provided that the dust masses transport mechanisms are properly known, the main dust sources can be identified, and therefore, appropriate actions can be taken. Therefore, the main goals of the present study are estimating dust concentration, determination of dust distribution with an emphasis on Iran (especially Tehran), and finding the main dust sources which will be followed in five steps. In the first step, by analyzing the measured data during dust observations in Tehran through 2013-2016, several simple and multivariate nonlinear regression models have been established in order...
Simulation of a Turbulent 3D Offset Jet
, M.Sc. Thesis Sharif University of Technology ; Farahanieh, Bijan (Supervisor) ; Afshin, Hossein (Supervisor)
Abstract
An offset jet refers to a flow issuing above a wall offset by a distance h and parallel to the axis of the jet. Asymmetric entrainment on both sides of the jet causes the jet to deflect toward the plate. The flow field of an offset jet is complex and is encountered in many engineering applications. For instance, burners, boilers, combustion chambers and fuel injection system are strongly governed by the behavior of offset jets. The understanding of the flow field properties of offset jet is required to ensure the proper design of systems.
In this study the mean flow and turbulent properties of 3D offset jet with circular nozzle, developing in a stagnant environment, are studied by means...
In this study the mean flow and turbulent properties of 3D offset jet with circular nozzle, developing in a stagnant environment, are studied by means...