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    Experimental Study of NanoFluid Heat Transfer in the Entrance Region

    , M.Sc. Thesis Sharif University of Technology Ezzati, Davoud (Author) ; Nouri Brojerdi, Ali (Supervisor)
    This project reports an experimental work on the convection heat transfer of nanofluids, made of -AL2O3 nanoparticles and de-ionized water, flowing through a copper tube in the laminar flow regime. The results showed considerable enhancement of convective heat transfer using the nanofluids. The enhancement was particularly significant in the entrance region, and was much higher than that solely due to the enhancement on thermal conduction. It was also shown that the classical Seider and Tate equation failed to predict the heat transfer behavior of nanofluids. Possible reasons for the enhancement were discussed. Migration of nanoparticles and the resulting disturbance of the boundary layer... 

    Nano-Fluid Natural Convection on a Constant Temperature Vertical Plate

    , M.Sc. Thesis Sharif University of Technology Iranmehr, Arash (Author) ; Nouri Boroujerdi, Ali (Supervisor)
    In the present study, Nano-fluid natural convection on a constant temperature vertical plate is numerically investigated, following the similarity analysis of transport equations. After changing the governing differential equations to the ordinary differential equations, they were numerically solved by the fourth order Runge-Kutta method.. The analysis shows that all three main profiles, velocity, temperature and concentration in their specific boundary layers, and the Prandtle number, depend on three important additional dimensionless parameters, namely a Brownian motion parameter, a thermophoresis parameter, and a buoyancy ratio parameter. Finally, it was found that the Nusselt number in... 

    Preparation of Nanofluid by Using Hybrid Nanostructures and Investigation of Thermal and Rheological Properties and Using it in the Petroleum Fluids

    , M.Sc. Thesis Sharif University of Technology Baghbanzadeh, Mohammad Ali (Author) ; Rashtchian , Davood (Supervisor) ; Rashidi, Alimorad (Supervisor) ; Lotfi, Roghayeh (Co-Advisor)
    In this study, thermal and rheological properties of nanofluids of water/carbon nanotubes, water/spherical silica nanoparticles and water/hybrid nanoparticles (hybrid of carbon nanotubes and spherical silica nanoparticles) have been investigated. To do so, carbon nanotubes have been synthesized by CCVD process and spherical silica nanoparticles and hybrid nanoparticles by wet chemical method. After synthesis of nanomaterials, nanofluids have been prepared by using SDBS as a dispersant with the concentration of 1.5 times of concentration of nanomaterials and then thermal conductivity, kinematic viscosity, dynamic viscosity and density of nanofluids have been investigated. As the results show,... 

    Investigation of Drop Phase Mass Transfer Coefficient During Rising Drops in a Pulse Sieved Plate Column in Presence of Nano Particles

    , M.Sc. Thesis Sharif University of Technology Khoobi, Nafiseh (Author) ; Bastani, Daruoosh (Supervisor) ; Bahmanyar, Hossein (Supervisor)
    Nanofluids are new engineering materials with great potential for application in process industries. Their enhanced heat-transfer properties are reported in recent literatures. However, with respect to the influence of nanoparticles on mass transfer characteristics, limited number of studies available in the literature, deal primarily with gas-liquid systems. In this work, mass transfer performance and droplet behavior along a pulsed liquid-liquid extraction column, is studied where SiO2 nanoparticles with concentrations of 0.01, 0.05 and 0.1 vol% and different hydrophobicities are applied to the dispersed phase. Using ultrasonication, nanoparticles were dispersed in kerosene as the base... 

    Analytical and Numerical Study of Dynamics of Wettability Driven Droplets in Smooth And Corrugated Channels

    , M.Sc. Thesis Sharif University of Technology Esmaili, Ehsan (Author) ; Moosavi, Ali (Supervisor)
    We studied dynamics of droplets inside channels under surface forces created by chemicalsteps on the channel walls. A multi-component Shan-Chen lattice Boltzmann method isused for this purpose.The effects of parameters such as the channel height, viscosity anddensity ratios on the results were investigated for homogeneous and grooved substrates. Alsoan analytical solution was developed for droplets under chemical heterogeneities in channels with smooth surfaces. The solution considers a general condition, namely, asymmetry of the contact angles on the top and bottom walls, the viscosity of the gas as the second fluid and the effect of the channel height. Then using Shan-Chen lattice... 

    Experimental and Theoretical Investigation on Thermal Conductivity of Combined Nanofluids

    , M.Sc. Thesis Sharif University of Technology Iranidokht, Vahid (Author) ; Shafii, Mohammad Behshad (Supervisor)
    Application of nanotechnology in the field of heat transfer has increased recently. The need to increase heat transfer rate yet decrease the size of cooling equipment, brought about lots of attention to thermal properties of Nanofluids. Nanofluid is the suspension of nanometer-sized solid particles in base liquid. Research on convective heat transfer of nanofluids which is only two decades old, shows great potential in increasing heat transfer rate. Although there is a remarkable research on thermal conductivity of Nanofluids, negligible research was conducted on combined Nanofluids . Developed Theory for thermal conductivity of combined nanofluid can be used to modeling the thermal... 

    Experimental Investigation of Mass Transfer Coefficient and Specific Interfacial Area in a New TIJR in the Presence of Nanoparticles

    , M.Sc. Thesis Sharif University of Technology Abdollahzadeh khanegha , Fariba (Author) ; Molaei Dehkordi, Asghar (Supervisor)
    The theory of mass transfer accompanied by chemical reaction for gas-liquid systems was used to measure the specific interfacial area and mass transfer coefficient in a two impinging jets reactor (TIJR) in the presence of γ-Al_2 O_3 nanoparticles.The absorption of oxygen in sulfite solutions used for the determination of mass transfer characteristics. First 3 liters of nanofluids were prepared at concentration of 1 w% then diluted To produce 10 Liters of nanofluids containing 0.3 w%. The stability of this nanofluid was determined using uv-vis to be less more than 95% in the first 3 hours. The influence of weight percent of nanoparticles (0, 0.05, 0.1, 0.15, 0.2, 0.3) on the specific... 

    Experimental Investigation of Pulsating Heat Pipe Using Nano-Fluid

    , M.Sc. Thesis Sharif University of Technology Taslimifar, Mehdi (Author) ; Saidi, Mohammad Hassan (Supervisor) ; Afshin, Hossain (Supervisor) ; Shafiee, Mohammad Behshad (Supervisor)
    Considerable increase in speed and decrease in size of electronic devices results in increase of heat flux, so there is a need to enhance efficiency of cooling electronic devices. In the present research two sets of OLPHPs with five turns for two different magnetic nano-fluids were fabricated and the effects of working fluid (water, and two types of magnetic nano-fluids), working pressure, concentration, magnetic field, magnets location, and inclination angle on the thermal performance of OLPHPs have been considered in both startup and steady thermal conditions.
    Experimental results show that magnetic nano-fluids can improve thermal performance of the OLPHPs. Application of magnetic... 

    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)
    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... 

    Evaluation and Simulation of using Magnetite as Heat Transfer Medium in Direct Solar Absorption Collectors

    , M.Sc. Thesis Sharif University of Technology Ebrahimi, Mahyar (Author) ; Mohammadi, Mohammad Reza (Supervisor)
    In this study, application of a Magnetic Nanofluid consisting of Magnetite as Nanoparticle and Water as base fluid in DASC systems is investigated. The DASC system is modeled theoretically and behavior of such system is predicted.In this study a comparison between magnetite Nanofluid and some other common Nanofluids is conducted. The study shows that Magnetite Nanofluid has a better performance and efficiency than Water, Al2O3 Nanofluid and SiO2 Nanofluid. Also magnetite Nanofluid and TiO2 Nanofluid function are almost similar.Also effect of external magnetic field on the performance of magnetite Nanofluid is investigated. It is showed that when the magnetic Nanofluid is subjected to an... 

    Investigation of Mass Transfer in Liquid-Liquid System in the Presence of Nanosized Particles

    , M.Sc. Thesis Sharif University of Technology Nakhaeipour, Fahimeh (Author) ; Bastani, Dariush (Supervisor)
    The main objective of this project is to study the effect of the presence of nanoparticles on mass transfer in liquid-liquid systems. To do this research, TiO2/water, Al2O3/water, CNTs/water and CNTs/toluene have been used as nanofluids. The experiments of TiO2/water nanofluid were been carried out in water-acetone-toluene system at two weigh percents of TiO2 nanoparticles. The result showed that mass transfer decreased in 0.5wt% of TiO2, compared to base fluid, and it increase in 1 %wt. Also in 0.5%wt the decrease in interfacial tension decreased diameter of drops and as a result mass transfer decreased too. In 1%wt the increase in viscosity increased the diameter of drops and then the... 

    Study on The Influence of Nanoparticles and Magnetic Field on The Liquid-Liquid Mass Transfer Coefficients

    , M.Sc. Thesis Sharif University of Technology Vahedi, Amid (Author) ; Molaei Dehkordi, Asghar (Supervisor)
    Magnetite (Fe3O4) nanoparticles were synthesized and coated with Oleic Acid using the co-precipitation method. The particles were characterized using DLS, FT-IR, SEM, XRD, VSM and UV-Vis spectrophotometry analysis. The mean size of particles was 28.8 nm and the FT-IR analysis indicated that Oleic Acid was coated suitably on the nanoparticles. The vsm test indicated no hysteresis loop for the particles, defining the superparamagnetism of them. A nanofluid containing nanoparticles in 5wt% Acetic Acid in Toluene as the base fliud was prepared. The stability of this nanofluid was determined using UV-Vis spectrophotometry to be less more then 95% in the first two hours. This nanofluid is used as... 

    Preparation of Nano Fluid from Carbon Nano Structures with High Surface Area in Order to Improve the Heat Transfer Coefficient in Heat Exchangers

    , M.Sc. Thesis Sharif University of Technology Naghash Chimeh, Amir Saleh (Author) ; Sattari, Sorena (Supervisor) ; Rashidi, Alimorad (Co-Advisor)
    In this research convective heat transfer coefficient enhancement of nanofluids prepared from high surface area graphene has been investigated in laminar flow in the developing region. The nanofluid has been prepared from nanoporous graphene with high surface area and with concentration of 0.025 to 0.1 %wt. Deionized water has been used as the base fluid and a type of Ter-Polymer has been utilized as the surfactant. The results indicate that thermal conductivity of nanofluid with concentration of 0.1 %wt remains quite constant, with only %3.8 enhancement, while convective heat transfer coefficient improves significantly, with 34% enhancement. The behavior of this enhancement related to the... 

    Mixed Convection of Magnetic Nanofluids in Channels Filled with a Porous Medium in the Presence of External Magnetic Field

    , Ph.D. Dissertation Sharif University of Technology Fadaei, Farzad (Author) ; Molaei, Asghar (Supervisor) ; Shahrokhi, Mohammad (Supervisor)
    In this research work, mixed convection heat transfer of ferrofluids (i.e., magnetite nanoparticle) in a circular pipe fully filled with a porous medium in the presence of constant and alternating magnetic fields has been investigated both numerically and experimentally. The duct was heated by a heating coil and the magnetic field was applied via four electromagnets with U shaped ferrite cores and a frequency inverter. The nanoparticles were synthesized using co-precipitation method and coated with a surfactant (i.e., Tween 80) and doubled distilled water was used as the base fluid. To characterize the synthesized nanoparticles, various analyzing techniques such as VSM, SEM, and XRD were... 

    Simulation of the Effects of Nanofluids on the Thermal Performance of a Heat Pipe

    , M.Sc. Thesis Sharif University of Technology Mirahmadi, Hamid Reza (Author) ; Moosavi, Ali (Supervisor) ; Kazemzadeh Hannani, Siamak (Co-Advisor)
    In terms of thermodynamics and heat transfer, heat pipes such as closed two-phase thermosyphon are of great importance in saving energy. In this study, a computational fluid dynamics model for simulation of a thermosyphon heat pipe with two-phase flow including phase change heat transfer was developed. The study has mainly focused on the effects of volume concentrations of Nanoparticles and the operating temperature on the heat transfer performance of the thermosyphon. The analysis was performed to compare heat transfer performance between a solid copper tube and a thermosyphon heat pipe which contained deionized water and graphene oxide(GO)/water Nanofluid as its working fluids. Based on a... 

    Numerical Study of Passive Heat Transfer Enhancement Methods in Automobile Radiator

    , M.Sc. Thesis Sharif University of Technology Asadollahi Shahbaboli, Pasha (Author) ; Mousavi, Ali (Supervisor)
    In this study, a three dimensional model of water-ethylene glycol based aluminum oxide nanofluid in the laminar flow of an automobile radiator has been numerically studied. The passive heat transfer enhancement method of twisted tape insertion in the flat tubes of radiator is used. The effects of different parameters on heat transfer and pressure drop have been investigated. Simulation results show that utilizing twisted tapes is an effective way of enhancing heat transfer in an automobile radiator. Despite the pressure drop penalty of using twisted tapes, the thermal performance factor which is a proper criteria for evaluating the practical use of the twisted tapes and considers the effect... 

    Determination of Parabolic Trough Solar Collector Efficiency Using Al2O3/Synthetic Oil Nanofluid: A Comprehensive Numerical Study with The Effect of Wind Velocity

    , Ph.D. Dissertation Sharif University of Technology Khakrah, Hamid Reza (Author) ; Shamloo, Amir (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)
    Due to significant reduction in fossil fuel sources; several researches have been conducted recently to explore modern sources of renewable energy. One of the major fields in the category of renewable energy harnessing devices is parabolic trough solar collectors (PTC). Several parameters have effect on the overall efficiency of the PTC’s.As the effect of these parameters is coupled to each other, a comprehensive investigation is necessary.In the present study a numerical analysis is performed to examine the efficiency of PTCs via variation of several governing parameters (e.g. wind velocity magnitude, nanoparticles volume fraction, inlet temperature and reflector’s orientation). A detailed... 

    Experimental Investigation Into the Performance of Pulsating Heat Pipe Using Nano-Encapsulated Phase Change Material Along with Rgo Nanosheets

    , M.Sc. Thesis Sharif University of Technology Mohammadi, Omid (Author) ; Shafii, Mohammad Behshad (Supervisor) ; Rezaee Shirin-Abadi, Abbas (Co-Supervisor)
    Heat pipes are useful devices in heat transfer, renewable energies and cooling systems in particular. According to various application of this systems in different industries, performance improvement of this devices has gained much importance. Working fluid is one of the effective factors on pulsating heat pipes. Since heat transfer in PHPs is natural convection and two-phase, specific heat and thermal conductivity of working fluid have an important role in the performance of pulsating heat pipes. In the present study, the effect of using nano-encapsulated PCM along with reduced graphene oxid (RGO) dispersed in water and their mixture as working fluid has on the performance of PHPs has been... 

    Ion Transport Through Graphene Fibers

    , M.Sc. Thesis Sharif University of Technology Ghanbari, Hamid Reza (Author) ; Esfandiar, Ali (Supervisor)
    Nanostructured graphene based membranes demonstrated excellent capabilities in various applications in nanofiltration and energy conversion due to unique atomically smooth surfaces and adjustable pore size or interlayers spacing at Angstrom scales.In addition to graphitic surface and physical confinement on ions in Graphene-oxide (GO) laminates, surface charges on such 2D-slits provide an attractive aspects to have more channels walls interactions with ions. There are some reports on the osmotic power generation using physical confinements and electrostatic interactions between ions and GO membranes. However, the results indicated insufficient power densities (1 W=m2 ) can be achieved... 

    Experimental and Numerical Investigation of Reactive Absorption in the presence of Nanofluid and Magnetic field

    , M.Sc. Thesis Sharif University of Technology Kheirkhah Ravandi, Zahra (Author) ; Molaei Dehkordi, Asghar (Supervisor)
    The importance of gases and liquids absorption in the liquid falling film is mostly due to the wide applications of liquid falling film reactors in the chemical industries. In such a reactor the mass and heat transfer occur simultaneously, but in most cases, the importance of mass transfer is predominant. Therefore, the study of heat transfer in this kind of reactor is neglected. In order to improve the efficiency of absorption, different methods have been employed by researchers. Owing to the rapid growth of nanotechnology, nanofluids have widely been used for increasing the absorption of solution, recently. Magnetic fluids due to their unique combination, among different kinds of...