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Total 47 records

    Improving the Cooling Performance of Automobile Radiator

    , M.Sc. Thesis Sharif University of Technology Habibiannejad, Hossein (Author) ; Afshin, Hossein (Supervisor)
    Abstract
    Inhencemant of automobile radiator heat performance is the purpose of this study. Radiator fin shape, coolant fluid properties and influence of nanofluid studied in this research. Plain fin, louvered fin and vortex generator fin is choosen and design. With flow simulation influence of fin shape on heat performance is studied. After that, with considering radiator coolant fluid, the effect of antifreezing on fin heat transfer is evaluated. Then by addin nanoparticles to water and antifreezing solution, effect of nanofluid on heat transfer is evaluated. Results show that with increasing the air velocity for all geometries in the study , heat transfer and pressure drop is increased. But heat... 

    Optimal Design of Cryogenic Heat Exchanger for Gas Liquefication Cycle

    , M.Sc. Thesis Sharif University of Technology Ebrahimi Ghalinghieh, Hamed (Author) ; Afshin, Hossein (Supervisor)
    Abstract
    Gas liquefication in low temperatures is one of the most challenging fields in engineering due to complexity of its thermodynamic analisys and fabrication of equipments. Heat Exchangers are one of the most important equipments in these prosseces. High prices of Heat Exchangers in these facilities makes their Optimal and cost effective design, of crucial importance. In this thesis three dimensional model of a Plate Fin Heat Exchanger is thoroughly investigated. Fistly, by means of Aspen Heat Exchanger design Software a counter flow Heat Exchanger is designed. This HX is to be placed in Collins cycle, so, working fluid in both hot and cold streams is Helium Gas. The HX then by means of ANSYS... 

    Experimental Study of Movement of Mercury Droplets in Micro Channel by Electromagnetic Force

    , M.Sc. Thesis Sharif University of Technology Ardeshir Larijani, Morteza (Author) ; Afshin, Hossein (Supervisor)
    Abstract
    As today's tremendous advance occurred in biotechnology and nanotechnology, the microfluidic devices made a new success that was not possible with the traditional equipments. It was useful in such a way that by using a microliter volume of that fluid, we could have the ability to use it in biologics, medicine, aerospace, cooling electronic systems and medical discovery. One of the main component of fluidic microsystems are micropumps in which they divide into two types. Reciprocating micropumps have been worked by stimulating electromagnetic micropumps which is based on Lorentz law. In this project, we try to investigate the impact of effective parameters in the movement of the mercury mass.... 

    Design and Performance Improvement of Distillation Column of Helium Purification Cycle

    , M.Sc. Thesis Sharif University of Technology Bayat, Mohammad (Author) ; Afshin, Hossein (Supervisor)
    Abstract
    Due to its unique properties, helium has extensive applications in various fields such as medicine, life sciences, electronic industries, welding, meteorology, and the industries which require low-temperature cooling. Also, designing the cryogenic distillation columns is one of the complex aspects of these plants. In the present study, the distillation column of a helium extraction plant from natural gas has been simulated by means of theta method of convergence. The required thermodynamic properties were determined from the Enhanced Predictive Peng-Robinson (E-PPR 78) equation of state, which has high accuracy in predicting the thermodynamic properties of natural gas componens. The... 

    Design and Simulation of Cryogenic Spiral Heat-exchanger for Gas Liquefaction Plant

    , M.Sc. Thesis Sharif University of Technology Rajabi, Vahid (Author) ; Afshin, Hossein (Supervisor)
    Abstract
    Heat exchangers are one of the most important components used in liquefaction cycles and overall efficiency of the cycle mainly depends on the heat exchangers effectiveness. It has been shown that the effectiveness of these equipments should be high enough to be able to liquefy a gas. Spiral heat exchangers are used frequently in cryogenic industry and specially in Helium liquefaction industry due to their specific characteristics, however according to literature review it turns out that little study is done in the field of simulation and geometrical parameter investigation of these kind of heat exchangers, so in this study the design and simulation of these cryogenics heat exchangers are... 

    An Economic Approach To Study & Optimization of Helium liquefier

    , M.Sc. Thesis Sharif University of Technology Mahmoudabad Bozchelou, Mohammad Amin (Author) ; Afshin, Hossein (Supervisor)
    Abstract
    Gas liquefaction is one of the main applications of Cryogenics science. Due to the unique properties of Helium, it is a strategic product in the world. Therefore, appropriate and applicable analysis should be used to investigate and optimize the Helium liquefaction cycles. In the current study, the goal is to find the optimal point with the help of energy and exergy analysis based on economic criterion, for the various parameters of Collins’ cycle. In order to simulate the cycle, a computer code is developed. First, sensitivity analysis of different parameters affecting the exergy efficiency and liquid fraction of the cycle has been done. Then, Artificial Neural Network and Genetic Algorithm... 

    Parametric Study and Numerical Simulation of Spiral Wound Heat Exchanger Performance at Cryogenic Temperatures

    , M.Sc. Thesis Sharif University of Technology Hosseinian Khorasgani, Mohsen (Author) ; Afshin, Hossein (Supervisor)
    Abstract
    Cryogenic is the study of physical phenomena at temperatures below 123 Kelvin. One of the applications of cryogenic science is the liquefaction of gases. In the liquefaction cycles of gases, such as helium liquefaction, fluidization occurs in the pressure reducing valve but temperature of the gas should be greatly reduced before it enters the pressure reducing valve. For this purpose, high-performance heat exchangers should be used. Spiral Wound is one of the heat exchangers that has ability to achieve over 90% efficiency due to its structure. Researchs in the field of design and simulation of spiral heat exchangers are limited and are done with a lot of simple assumptions such as constant... 

    Experimental Investigation on the Accelerated Motion of Newtonian and Non-Newtonian Liquid Drops

    , M.Sc. Thesis Sharif University of Technology Aminzadeh, Milad (Author) ; 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... 

    Simulation of Air to Air Plate Heat Exchangers to Investigate the Effects of Baffle Location, Header and Fins Geometry in their Performance

    , M.Sc. Thesis Sharif University of Technology Salehi, Sina (Author) ; Afshin, Hossein (Supervisor) ; Farhanieh, Bijan (Supervisor)
    Abstract
    Many studies have been conducted in plate heat exchangers. However, some effective parameters on the performance have been less considered. It has been demonstrated that heat exchanger performance increases with more uniform flow distribution. It is possible to make the flow distribution more uniform by installing a baffle inside the header. The ‘gap’ or the distance between this baffle and the inlet is one of the important parameters in determining performance but is has been mostly overlooked by previous studies. This study investigates the effects of inlet baffle place on heat exchanger performance. Another important factor is the header geometry. Elongation and reduction in header... 

    Simulation of a Turbulent 3D Offset Jet

    , M.Sc. Thesis Sharif University of Technology Mohammad Aliha, Negar (Author) ; 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... 

    Experimental Study on Behavior of Turbidity Currents with Obstacle

    , M.Sc. Thesis Sharif University of Technology Oshaghi, Mohammad Reza (Author) ; Afshin, Hossein (Supervisor) ; Firoozabadi, Bahar (Co-Advisor)
    Abstract
    Turbidity currents are produced when a particle laden fluid flows under the lighter ambient fresh fluid. The streaming of particle laden fluid is called turbidity current and this kind of currents is the major mechanism for sediment transportations in lakes and oceans. In the present research, the main concentration is on the effect of obstacle on the behavior of turbidity current. A series of laboratory experiments were carried out with various obstacle heights, shapes and different inlet densimetric Froude numbers. In each experiment, velocity profiles upstream and downstream of the obstacle were measured, using an ADV (Acoustic Doppler Velocimeter). Kaolin was used as the suspended... 

    Design and Performance Analysis of a Reversible Axial Flow Fan and Study of Symmetric Profile Effects

    , M.Sc. Thesis Sharif University of Technology Soltanian, Salman (Author) ; 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... 

    Three-Dimensional Large Eddy Simulation of Continuous Density Currents

    , M.Sc. Thesis Sharif University of Technology Najafpour, Nategheh (Author) ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Co-Advisor)
    Abstract
    When a fluid moves inside another fluid while they have unequal density, a phenomena occurs which is called density (or gravity) current. Therefore density difference and gravity are key factors of density current generation. Due to application in engineering and geology, it is essential to investigate and analyze the above mentioned phenomena. Dam reservoirs, sandstorm in deserts, snow slide onset and falling, ash clouds produced during eruption of a volcano, and spreading of density current due to the collapsing of reservoirs are some examples of gravity current. There are lots of methods to simulate the turbulence of density current like DNS or RANS. But DNS has high computational cost... 

    Numerical Modeling of Drop Formation and Deformation using the Finite Volume Method

    , M.Sc. Thesis Sharif University of Technology Sadat Salehi, Moloud (Author) ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Co-Advisor)
    Abstract
    Drop formation from the tip of a nozzle and its motion in bulk fluid is an interesting and practical process which has widely turned researchers’ attention. Investigation into the governing physics and effective parameters on formation, deformation and motion of a drop increases the efficiency of the related industrial processes. Thus in the present study, in order to simulate this process, full Navier-Stokes equations solved by the Volume of Fluid (VOF) method in an axisymmetric domain using Fluent software as the solver. In this research, the effects of Weber number (the proportion of inertial force to surface tension force) and Ohnesorge number (which refers to the proportion of viscous... 

    Bladeless Fan Design

    , M.Sc. Thesis Sharif University of Technology Jafari, Mohammad (Author) ; Afshin, Hossein (Supervisor) ; Farhanieh, Bijan (Co-Advisor)
    Abstract
    In the present study, performance of a novel fan namely bladeless fan has been evaluated. The aerodynamic and aeroacoustic performances are studied by using 3D simulation of this fan. Mass conservation equation, momentum conservation equations and noise equations of FfowcsWilliams-Hawkings numerically solved to investigate performance of this fan. Firstly, fan cross section profile was designed by Eppler airfoil 473 instead of the prior profile as a modification then effect of different geometrical parameters on the performance is examined. These parameters are height of cross section, angle of output flow with respect to fan axis, thickness of output airflow, hydraulic diameter and aspect... 

    Numerical Simulation of the Air Pollution Dispersion to the Neighboring Regions of Traffic Tunnel Portals

    , M.Sc. Thesis Sharif University of Technology Nemati Mehr, Mahdi (Author) ; Afshin, Hossein (Supervisor) ; Hosseini, Vahid (Co-Advisor)
    Abstract
    By expansion of urban areas and increasing in number of vehicles commuting, tunnels are one of the most inevitable part for developing urban areas. Nevertheless, one of the important topics about tunnels is exhaustion of polluted air into its surroundings. Tohid Tunnel, stretching about 2136 meter, is currently the longest urban tunnel in Iran, connecting Chamran and Navvab Highway from north of Fatemi street, to the Shokufeh street. Now, exhausting pollutants is done only by north and south portals beside a middle shaft. The purpose of this project is to analyze pollutant dispersion from south portal of Tohid tunnel which is located in Navvab residential region. This is done by considering... 

    Large Eddy Simulation of Continuous Density Current Impinging on Obstacles

    , M.Sc. Thesis Sharif University of Technology Abbaszadeh, Shahabaddin (Author) ; Firoozabadi , Bahar (Supervisor) ; Afshin, Hossein (Supervisor)
    Abstract
    Density currents as a particular form of stratified fluid motion in nature have attracted the interest of many researchers in the past decades. These flows are formed whenever a fluid with specific density begins to move through another fluid with different density called ambient fluid. Prediction of propagation of turbulent density currents, especially because of their remarkable influence on the environment, is one of the researcher’s interests in geophysics and engineering. Density currents have a lot of applications in industry and nature. Sand storm in deserts, turbidity currents in oceans and avalanches are natural examples and leakage of dense gas into the atmosphere due to reservoir... 

    Experimental Investigation of Mass Transfer by Droplet Using Image Processing

    , M.Sc. Thesis Sharif University of Technology Babak, Pirooz Hashemi (Author) ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Co-Advisor)
    Abstract
    Wide and varied aspects of droplet motion due to its increasing application in various fields has attracted much attention. Analysis of mass transfer from the liquid drop into the other fluid, such as complex and intriguing problems in fluid mechanics, which is very important. Many experimental and numerical studies have been carried out in this case that the evelopment of laboratory equipment and software, are rapidly growing.
    In this study, given the importance of this issue, experimental study on mass transfer in fluid systems solution droplet liquid - liquid extraction, have been considered. Different methods have been discussed to date. In the present study, using image processing... 

    Experimental Study on Behavior of Particle-Laden Density Current over Obstacles

    , M.Sc. Thesis Sharif University of Technology Yaghoubi, Sina (Author) ; Afshin, Hossein (Supervisor) ; Firoozabadi, Bahar (Co-Advisor)
    Abstract
    Density currents, caused by the intrusion of dense fluids under lighter ambient fluids, frequently occur in both natural and industrial situations. As a result of the density differences, the driving force can arise from soluble substances, temperature differences, etc. If the driving force comes from suspended particles including silt and mud, the currents are called turbidity currents. Due to the variation in concentration and the consequent driving force along the flow path, turbidity currents are significantly more complicated than saline currents. These currents play the most important role in sedimentation in lakes, seas and oceans. In addition, turbidity currents are the main factor... 

    Numerical Simulation of Spray and Combustion in a Gasoline Direct Injection (GDI) Engine

    , M.Sc. Thesis Sharif University of Technology Zamani Haghighi, Hamed (Author) ; 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...