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    A new approach for calculation of relaxation time and magnetic anisotropy of ferrofluids containing superparmagnetic nanoparticles

    , Article Journal of Mining and Metallurgy, Section B: Metallurgy ; Volume 48, Issue 1 , 2012 , Pages 81-88 ; 14505339 (ISSN) Ahmadi, R ; Hosseini, H. R. M ; Sharif University of Technology
    2012
    Abstract
    In this work, a new approach is described for the calculation of the relaxation time and magnetic anisotropy energy of magnetic nanoparticles. Ferrofluids containing monodispersed magnetite nanoparticles were synthesized via hydrothermal method and then heated using the 10 kA/m external AC magnetic fields in three different frequencies: 10, 50 and 100 kHz. By measuring the temperature variations during the application of the magnetic field, the total magnetic time constant including both Brownian and Neel relaxation times can be calculated. By measuring the magnetic core size and hydrodynamic size of particles, the magnetic anisotropy can be calculated too. Synthesized ferrofluids were... 

    Experimental and numerical investigation of fully developed forced convection of water-based Fe3O4 nanofluid passing through a tube in the presence of an alternating magnetic field

    , Article Advances in Mechanical Engineering ; Volume 7, Issue 2 , February , 2015 , Pages 1-9 ; 16878132 (ISSN) Dibaei Bonab, M. H ; Shafii, M. B ; Nobakhti, M. H ; Sharif University of Technology
    Hindawi Publishing Corporation  2015
    Abstract
    The effect of a magnetic field on the fully developed forced convection of Fe3O4 flow inside a copper tube is experimentally and numerically investigated. The flow is assumed to be under uniform heat flux. This study aims to examine the effects of the nanoparticle volume fraction, as well as alternating magnetic field strength and frequency, on the convective heat transfer for different Reynolds numbers. To ensure accuracy, the numerical results are validated by empirical results with similar geometry and boundary conditions. A satisfying agreement was achieved. The results show that the heat transfer increases with increase in alternating magnetic field frequency but... 

    Intensification of heat transfer rate in a rectangular channel equipped with pins, using non-uniform magnetic field

    , Article Journal of Nanofluids ; Volume 8, Issue 5 , 2019 , Pages 1041-1050 ; 2169432X (ISSN) Mokhtari, M ; Hariri, S ; Sharif University of Technology
    American Scientific Publishers  2019
    Abstract
    In the present study, numerical simulation is used to evaluate the influence of the non-uniform magnetic field on the heat transfer of magnetic nanofluids inside a pinned channel. This article focused on the flow pattern and heat transfer of water-based nanofluids in the presence of a wire in a three-dimensional geometry. In this work, the fluid flow is laminar and constant heat flux is applied on the wall of the channel. A wire in various orientations, in comparison with the axis of the channel, generates the magnetic field. The base fluid is water and Nano-particles (Fe3O4 and Fe) add to base fluid with different volume concentrations (0, 0.5, 1%). The computational fluids dynamic is used... 

    Experimental study of internal forced convection of ferrofluid flow in porous media

    , Article Defect and Diffusion Forum ; Vol. 348 , April , 2014 , pp. 139-146 ; ISSN: 10120386 ; ISBN: 9783038350002 Sehat, A ; Sadrhosseini, H ; Shafii, M. B ; Sharif University of Technology
    Abstract
    This work presents an experimental study of the effect of a magnetic field on laminar forced convection of a ferrofluid flowing in a tube filled with permeable material. The walls of the tube are subjected to a uniform heat flux and the permeable bed consists of uniform spheres of 3-mm diameter. The ferrofluid synthesis is based on reacting iron (II) and iron (III) in an aqueous ammonia solution to form magnetite, Fe3O4. The magnetite is mixed with aqueous tetra methyl ammonium hydroxide, (CH3) 4NOH, solution. The dependency of the pressure drop on the volume fraction, and comparison of the pressure drop and the temperature distribution of the tube wall is studied. Also comparison of the... 

    Experimental study of internal forced convection of ferrofluid flow in non-magnetizable/magnetizable porous media

    , Article Experimental Thermal and Fluid Science ; Volume 96 , 2018 , Pages 441-450 ; 08941777 (ISSN) Shafii, M. B ; Keshavarz, M ; Sharif University of Technology
    Elsevier Inc  2018
    Abstract
    In this work, the thermal and hydrodynamic performance of ferromagnetic fluid, which flows through a copper tube in thermal entrance region, has been studied. The flow in the tube is laminar and subjected to constant heat flux. A part of the tube contains a porous medium with paramagnetic properties and porosity of 0.46. Ferrofluid is composed of Fe3o4 and water with (CH3)4NOH as a surfactant that is prepared in three different volume fractions. The effects of constant and oscillating magnetic fields on convective heat transfer coefficient were examined for various Reynolds numbers, frequencies and volume fractions. The results show that the maximum enhancements of average heat transfer... 

    Study on the Influence of Nanoparticle and Magnetic Field on Flow in Porous Media

    , M.Sc. Thesis Sharif University of Technology Jafari, Amin (Author) ; 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... 

    Design and Fabrication of a Ferrofluidic Miniature Pump

    , Ph.D. Dissertation Sharif University of Technology Ashouri, Majid (Author) ; Shafii, Mohammad Behshad (Supervisor) ; Moosavi, Ali (Supervisor)
    Abstract
    This thesis presents the prototype design and fabrication of magnetically actuated miniature pumps which utilize self-sealing capability of ferrofluid-covered permanent magnets in both pumping and valving mechanisms. The contactless external actuation feature of the design enables integration of the pump with other PMMA-based microfluidic systems with low cost and disposability. The body of the 1st fabricated prototype pump consists of three nozzle/diffuser elements and two pumping chambers connected to the ends of a flat-wall pumping cylinder. A cylindrical permanent magnet placed inside the pumping cylinder acts as a piston which reciprocates by using an external magnetic actuator driven... 

    Synthesis and Biological Evaluation of Magnetic Colloids of Ultrasmall Super Paramgnetic Iron Oxide Nanoparticles for Biomedical Applications

    , M.Sc. Thesis Sharif University of Technology Abedini, Fatemeh (Author) ; Maddah Hosseini, Hamid Reza (Supervisor) ; Shokrgozar, Mohammad Ali (Supervisor)
    Abstract
    Present study is designed to determine the effect of manganese content in primitive inverse spinel structure of iron oxide nanoparticles. PEG coated water base ferrofluids of Mnx¬Fe3-xO4 (0<0>1)nanoparticles were prepared by co-precipitation method in presence of nitrogen gas and ultrasonic waves using NaOH as a base for biomedical purposes. The crystallite size and structure of synthesized nanoparticles were studied using atomic absorption spectroscopy (AAS), X-ray diffraction spectrometry (XRD), field emission scanning electron microscopy (FE-SEM) and dynamic light scattering (DLS) methods. Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) were used to... 

    Performance Investigation of a Diesel Engine Using Nano Particles

    , M.Sc. Thesis Sharif University of Technology Daneshvar, Fariborz (Author) ; Shafii, Mohammad Behshad (Supervisor) ; Saboohi, Yadollah (Supervisor) ; Mobini, Kamran (Supervisor)
    Abstract
    In this Study, experimental tests were carried out to investigate the effects of adding water-based ferrofluid to diesel fuel in a diesel engine. These effects included the combustion performance and exhaust emission characteristics of the diesel engine. To this end, emulsified diesel fuels of 0, 0.4, and 0.8 ferrofluid/Diesel ratios by volume were used in a four stroke diesel engine. The results indicate that adding ferrofluid to diesel fuel has a perceptible effect on engine performance, increasing the brake thermal efficiency and decreasing the brake specific fuel consumption as compared to diesel fuel. Furthermore, adding ferrofluid to diesel fuel increased the exhaust gaseous... 

    Experimental Study of Pool Boiling Heat Transfer Enhancement by Presence of Magnetic Particles under the Influence of Magnetic Field

    , M.Sc. Thesis Sharif University of Technology Feizbakhshi, Morteza (Author) ; Behshad Shafii, Mohammad (Supervisor)
    Abstract
    Study on pool boiling heat transfer characteristics of water-based magnetic fluid and distilled water containing micro size particles has performed. Different concentration in each experiment has been studied to investigate the effect of magnetic fluid and micro size particles on boiling heat transfer on horizontal plate heater. The nickel particles was used as micro size particles which is expected to increase thermal performance of water due to high thermal conductivity of nickel. Experimental results showed adding nickel micro size particles to water can deteriorate the boiling heat transfer coefficient. However the amount of deterioration was the same for all concentrations of nickel... 

    Investigation of the Geometry Effect on Electrokinetic Instability in Microflows

    , M.Sc. Thesis Sharif University of Technology Mohammadzadeh, Alireza (Author) ; Saidi, Mohammad Hassan (Supervisor)
    Abstract
    Lab-on-a-chip devices have gained a lot of attention in chemical and biomedical analyses during the past two decades. These devices employ microfluidics basics and fundamentals to combine multifold laboratory processes in one single portable chip. The electric field has been often used in most microfluidics applications for the ease of sample control as well as become easily integrated to other chip components. Instabilities in microflows would occur when two fluids of different electric properties are exposed to an adequately strong electric field. Studying these electrokinetic instabilities is not only important for the fundamental studies but also for practical applications in micromixers... 

    Design and Fabrication of a Fluid Oscillation Micro-Power Generator in a Pulsating Heat Pipe and its Performance Experimental and Theoretical Investigation

    , M.Sc. Thesis Sharif University of Technology Zia Oleslami, Naser (Author) ; Shafii, Mohammad Behshad (Supervisor)
    Abstract
    Pulsating heat pipes have been more studied in recent two decades as effective tools in dissipating waste heat from electronic components. Due to oscillating fluid flow model, these tubes have the potential of converting waste energy to power. This research presents a system that makes this potential to act. In this system, the oscillating slug-plug fluid flow pattern in an open-looped pulsating heat pipe makes a permanent magnet which is levitated in Ferrofluid to vibrate in an electromagnetic vibration-based generator in order to induce electro motive force. The fluid flow regime in pulsating heat pipe has been simulated numerically with finite element scheme. The model results for fluid... 

    Fabrication of Ferrofluidic Micropump

    , M.Sc. Thesis Sharif University of Technology Ashouri, Majid (Author) ; Shafii, Mohammad Behshad (Supervisor) ; Saidi, Mohammad Said (Supervisor) ; Saidi, Mohammad Hassan (Supervisor)
    Abstract
    In this project, two Ferrofluidic micropumps that do not need any mechanical moving parts are presented. These micropumps are including simple microchannels containing magnetic fluid plugs that are used as flow actuator and the on/off valve. Using external magnetic field actuation in this type of micropumps, the magnetic fluid would have continuous motion in a channel with micrometer dimensions that would provide the main fluid to be pumped. Although the plug of magnetic fluid has surface contact with operative fluid, but considering its specific features, it would not compine with the pumping fluid. These micropumps may be used to pump the fluids or gases. The outcomes of the investigation... 

    Design and Fabrication of Reciprocating Micropumps with Actuated Fluid Slug

    , M.Sc. Thesis Sharif University of Technology Amiri Hezave, Hamid (Author) ; Shafii, Mohammad Behshad (Supervisor)
    Abstract
    Design, fabrication and performance of the reciprocating micropumps with actuated fluid slug have been investigated. In these micropumps, pumping principle is based on reciprocating movement of a fluid slug. The fluid slug must be conductive in magnetohydrodaynamic micropump to be actuated by Lorentz force and have good magnetic properties in ferrofluidic micropumps to be actuated by an external magnetic field.
    On the other hand, a theory is developed in ahead of design and fabrication process to diagnose the critical and the most influential parameters. Magnetohydrodynamic micropumps in 4 distinict design using nozzle-diffuser element, passive ball valve and active mercury valve have... 

    Synthesis and Biological Evaluation of Superparamagnetic Iron Oxide Nanoparticles as Contrast Agents for Bioimaging Applications

    , M.Sc. Thesis Sharif University of Technology Ali Abouzar, Mitra (Author) ; Maddah Hosseini, Hamid (Supervisor) ; Oghabian, Mohammad Ali (Supervisor)
    Abstract
    A biocompatible ferrofluid containing ?Fe?_3 O_4 nanoparticles was produced using co precipitation of ?FeCl?_2.?4H?_(2 )O and ?FeCl?_3 ?6H?_2 O under ultrasonic irradiation power with NaOH being the alkaline. Two variables studied in this research were concentration and molecular weight of PEG, as the coating agent. The impact of these variables were carefully monitored on shape, size distribution and magnetic behavior of nanoparticles through SEM, DLS, XRD and VSM characterization techniques. Moreover, MRI relaxation times,T_1and T_2, were calculated using synthesized nanoparticles as contrast agents. Accordingly these nanoparticles were biologically evaluated by MTT assay. Results... 

    Experimental Investigation on Laminar Forced Convection Heat Transfer of Ferrofluids Under an Alternating Magnetic Field

    , M.Sc. Thesis Sharif University of Technology Ghofrani, Ali (Author) ; Shafii, Mohammad Behshad (Supervisor)
    Abstract
    This research study presents an experimental investigation on forced convection heat transfer of an aqueous ferrofluid flow passing through a circular copper tube in the presence of an alternating magnetic field. The flow passes through the tube under a uniform heat flux and laminar flow conditions. The primary objective was to intensify the particle migration and disturbance of the boundary layer by utilizing the magnetic field effect on the nanoparticles for more heat transfer enhancement. Complicated convection regimes caused by interactions between magnetic nanoparticles under various conditions were studied. The process of heat transfer was examined with different volume concentrations... 

    Fabrication and Experimental Investigation of Micro Heat Pipe Using Ferrofluid Under Magnetic Field

    , M.Sc. Thesis Sharif University of Technology Jahani, Nariman (Author) ; Shafii, Mohammad Behshad (Supervisor)
    Abstract

    On track to achieve heat transfer methods for small-scale, this research describes the design process of fabrication and experimental analysis of micro heat pipes with a rectangular section. First, the overview of micro-fluid systems and conventional mechanisms of heat transfer in these systems is discussed. Then, in order to describe the research theory and principles of heat pipe, various types of heat pipes micro scale and macro scaled are analyzed. After that, the method used for fabrication of a micro heat pipe without grooves is described. A new method for fabrication of MHP is investigated in this study. By using this method, one fiber glass board is fabricated by printed circuit... 

    Experimental Study of Internal Forced Convection of Ferrofluid Flow in Porous Media

    , M.Sc. Thesis Sharif University of Technology Sehat, Ashkan (Author) ; Sadrhosseini, Hani (Supervisor) ; Shafii, Mohammad Behshad (Co-Advisor)
    Abstract
    The present work illustrates the results of an experimental study of ferrofluid flow in a tube subjected to a constant heat flux on its wall and filled with permeable material under the effect of magnetic field. The aim of this project is investigating the enhancement of heat transfer and obtaining a uniform temperature distribution inside the pipe. In order to achieve this, a porous medium with a porosity of 0.39 and ferrofluid with volume fractions of 0.6, 1.0 and 1.5 are used simultaneously, in the presence of magnetic field. The experiments are held for four different Reynolds numbers of 147.1, 167.3, 184.3 and 205.1. Also, four various modes of the oscillatory magnetic field are applied... 

    , M.Sc. Thesis Sharif University of Technology Azimi, Saloomeh (Author) ; Maddah Hosseini, Hamid Reza (Supervisor)
    Abstract
    A biocompatible ferrofluid have been prepared by co-precipitation of FeCl2.4H2O and FeCl3.6H2O under ultrasonic irradiation and with NaOH as alkaline agent. Also cystein was used as capping agent in the solution. Magnetic properties of the produced ferrofluid then determined by VSM test and magnetite nanoparticles were characterized by XRD and TEM techniques. Results indicate the presence of a biocompatible superparamagnetic ferrofluid including magnetite nanoparticles with particle size ranging under 15 nm. The effect of ultrasonic irradiation on presence of a sharp particle size distribution then denoted by comparing the condition with production without ultrasonic irradiation  

    Investigation of Micro Heat Pipe Performance Using Nano-Fluid as Working Fluid

    , M.Sc. Thesis Sharif University of Technology Jahani, Kambiz (Author) ; shafii, Mohammad Behshad (Supervisor) ; Saboohi, Yadollah (Co-Advisor)
    Abstract
    Thermal management of micro-electronic devices is a contemporary issue which is increasingly gaining importance in line with the advances in packaging technology. Immediate and consistent multi-disciplinary research is needed to cater to the prevailing trends of net power and flux levels of upcoming micro-electronics products. Material science, packaging concepts, fabrication technology and novel cooling strategies are some of the key areas requiring synchronal research for successful thermal management. Focusing on the latter area, this thesis presents an experimental study on thermal performance of Micro-Closed Loop Pulsating Heat Pipes (MCLPHPs) which are new entrants in the family of...