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heat-transfer
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Experimental of Convective Heat Transfer Coefficient Around a Vertical Rod Bundle
, M.Sc. Thesis Sharif University of Technology ; Jafari, Jalil (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)
Abstract
Research on convective heat transfer coefficient around a rod bundle has several applications in industry. So far, many studies have been conducted in correlations related to internal fully developed flow. By comparing Dittus-Boelter, Sieder-Tate and Petukhov found to be more practical. The present study examines the validity of these frequently applied correlations experimentally. A thermohydraulic loop has been designed and manufactured to test and measuring the convective heat transfer coefficient. Due to its generalizibility, the unique geometry of this test facility (hexagonal arranged, 7 vertical rods in a hexagonal tube) has achieved extensive application. The major deviation factors...
Experimental Investigation of Nano Particle Effect on Heat Transfer in a Micro Heat Exchanger
, M.Sc. Thesis Sharif University of Technology ; Shafii, Mohammad Behshad (Supervisor) ; Saidi, Mohammad Hassan (Supervisor) ; Saeedi, Mohammad Saeed (Supervisor)
Abstract
Modern microelectronic systems generate a large amount of heat which must be transferred out of the system without excessive temperature rise. Conventional forced air convection and microchannel cooling plates have reached their performance limits Nanofiuids are proposed as an innovative way to solve the problem. A nanofiuid is nanoscale solid particles dispersed in a traditional heat transfer liquid. Some studies show an anomalous increase in the thermal conductivity for stationary nanofiuids. However, there are only few previous studies on the convection heat transfer rate and viscosity of nanofiuids. Both convection and stationary measurements of the thermal conductivity are widely...
Direct Numerical Simulation of Heat and Fluid Flow through Porous Channel
, M.Sc. Thesis Sharif University of Technology ; Nouri Boroujerdi, Ali (Supervisor)
Abstract
In this project, direct numerical simulation of fluid flow inside the porous channel is carried out. The flow channel is containing uniform array of solid blocks with square cross sections in an staggered scheme. Two thermal boundary conditions of constant temperature and constant heat flux of solid blocks were applied to the problem. The Navier-Stokes equations directly applied to the fluid region with no assumption of volume-averaging. Governing equations of two-dimensional flow with constant properties were discretized with control volume method. Energy equations for solid and fluid phases were solved separately. The results show that for solid block lengths over channel height, a/H=0.05,...
Experimental and Analytical Study of Warpage Reduction in Polypropylene 3d Printing by using Recycled Silica Nanoparticles
, M.Sc. Thesis Sharif University of Technology ; Pircheraghi, Gholamreza (Supervisor) ; Tavakoli, Rohollah (Supervisor)
Abstract
Creating sustainable development in today's society is essential, and one of the most important elements to achieve this is the phenomenon of recycling. Lead-acid batteries are one of the sources of environmental pollution, and their separators contain 50% recyclable silica nanoparticles. In this research, impurities in these separators were removed using two methods: washing with water and sandblasting. The purity of recycled nanoparticles was 85.5% in the first method and 98% in the second method. In addition to the importance of recycling, finding a suitable use for recycled materials is also critical. FDM 3D printing is a new method of producing parts, but polypropylene is not commonly...
Optimal Heat Transfer in Composite Plates Insulation Matrix Reinforced with Non-Homogeneous Conductive Materials
, M.Sc. Thesis Sharif University of Technology ; Tavakoli, Rohollah (Supervisor)
Abstract
In order to heat, cool or control the heat transfer in insulation plates, under a certain loading condition, for uniformity temperature distribution and maximum temperature control, it is possible to composite materials with high thermal conductivity and appropriate distribution in Inside the insulation matrix. The purpose of this study is to provide a method for optimally distributing conductive phase inside an insulating plate under a specific thermal loading condition so that the temperature difference between the various points of the plate is minimized in stable conditions. For this purpose, a topology optimization method was used to determine the optimal distribution of conductive...
Thermal Simulation of Sponge Iron Production by Höganäs Method
, M.Sc. Thesis Sharif University of Technology ; Halali, Mohammad (Supervisor)
Abstract
Sponge Iron production is conducted in various methods that one of them is using coal as a reduction agent. Hoganas process is a different coal-based method that has not been investigated in details. Therefore, the heat transfer method in the system is one of the basic steps to a better recognition of this process (with special Hoganas charging). The present paper investigates the temperature distribution method in the Hoganas cylinder through a numerical model using finite elements. The effects of different parameters, namely preheating and porosity were studied on ceramic crucible made from silicon carbide and it was observed that the consumption energy decreases with the increase of...
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
In recent years, different of nanoparticles as oil additives has been investigated in many studies . These research show that nanoparticles are deposited on the surface friction and improve tribology properties of base oil and also significant reduction of wear and friction caused by the nanoparticles. Compared with metal and metal oxide nanoparticles , carbon nanotubes (CNT) due to the high thermal conductivity and high aspect ratio , is an excellent candidate as the nanoparticle is dispersed . For preparing useful oil it is essential to stabilize nanoparticles in fluid that will not settle over long time . Oils containing nanoparticles by increasing the heat transfer coefficient...
Heat Transfer Modelling and Mechanical Properties Of Wide-Gap Thermite Rail Welds
, Ph.D. Dissertation Sharif University of Technology ; Kokabi, Amir Hossain (Supervisor) ; Davami, Parviz (Supervisor)
Abstract
Wide-gap aluminothermic rail welds with root opening of 60 mm were produced using plain carbon steel rail and non-alloy aluminothermic charge. Such process can repair defective rails, each with only one wide-gap weld instead of using a relatively long plug rail and two standard welds which reduces number of welds in railways and cause saving in money. Required equipments including metallic and sand molds, crucible and self-tapping thimble were designed. Mechanical properties and micro-structure of rail welds and corresponding heat affected zones as well as impact energies and fracture toughnesses of welds were investigated. Wide-gap aluminothermic rail welds exhibited 98% and 95% of yield...
Modeling Evaluation of Pressure Effect on Mold/Metal Interface Heat Transfer Coefficient in A356 Alloy
, M.Sc. Thesis Sharif University of Technology ; Varahram, Nasser (Supervisor) ; Davami, Parviz (Supervisor)
Abstract
Mold/metal interfacial heat transfer coefficient (IHTC) is the most important parameter that influences the solidification and the mechanical properties of a solidified product. The present work focuses on the determination and evaluation of pressure effect on interfacial heat transfer coefficient from the experimental cooling curves during unidirectional solidification of A356 alloy against water cooled Gray iron mold (chill). For this purpose, inverse heat conduction method is used. The results showed that IHTC is not constant, but varies with time, temperature and pressure during solidification. IHTC variation is related to coherency and critical solid fraction during...
Simulation of Exothermic and Insulated Materials Effect on Increasing Efficiency of feeder in Gray Cast Iron
, M.Sc. Thesis Sharif University of Technology ; Davami, Parviz (Supervisor) ; Varahram, Naser (Supervisor)
Abstract
The use of exothermic and insulated materials is one of the most effective methods in increasing feed efficiency. In order to model performance of these materials, we need for information in connection with thermo physical properties, interface resistances and way for releasing heat in exothermic and insulated materials. Due to lack of published information in this area, the purpose of this study is for increasing information in this area and especially in the heat release in these materials. In this investigation first, physical model governing this phenomenon was found. At this stage in order to Model of heat transfer from one dimensional transient heat conduction equation, discreted by...
Modelling of Pressure Effect on Metal/Mold Interface Resistance in the A356 Aluminium Alloy Casting Process
, M.Sc. Thesis Sharif University of Technology ; Davami, Parviz (Supervisor) ; Varahram, Naser (Supervisor)
Abstract
The computer simulation of freezing patterns in castings has done much to broaden our understanding of casting and mold system design. The structural integrity of shaped castings is closely related to the time–temperature history during solidification, and the use of casting simulation could do much to increase this knowledge in the foundry industry. However, some uncertainties must be eradicated, particularly heat transfer at the metal/mold interface. The accurate knowledge of interfacial heat transfer coefficients is necessary for accurate modeling of castings. The present work focuses on the determination of transient mold–environment and metal–mold heat transfer coefficients during...
Dynamic Modeling of Top-Fired Steam Methane Reforming Furnaces
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Fathollah (Supervisor) ; Vafa, Ehsan (Supervisor)
Abstract
CFD models are accurate but time-consuming for simulation and optimization of steam methane reformer and controlling the tube wall temperature, and syngas production rate and unsuitable for online optimization. Empirical data-driven models are less accurate when there are wide variations in operating conditions. The physics-based model presented in this thesis overcomes these limitations. In this model, the furnace side and the process side are divided into zones with uniform temperature and composition, and for each zone, mass, energy and momentum balances are derived. Radiative heat transfer modeling and calculation of exchange areas are accomplished with the zone method. The system of...
Drying in Spouted Beds with Draft Tube
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
Simulation runs have been conducted to predict the evolution of sand drying in conical spouted beds with a non-porous draft tube. In the simulation runs, the moisture content of the solid phase was assumed to be 7 % (kg water/kg sand). The simulation results were validated against experimental results reported by Olazar et al. and good agreement was obtained.Influences of various physical and geometrical parameters such as superficial gas velocity, inlet temperature, length and diameter of draft tube and initial moisture content on the sand drying were investigated. Temperature and gas velocity are the most important parameters for improving the drying process and reduce the drying time of...
Optimal Design of Energy Supply Units Using Solar Energy
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Fathollah (Supervisor) ; Bozorgmehri Boozargomehri, Ramin (Supervisor)
Abstract
The sun, as the world's largest source of energy, had always affected various aspects of human life. Several studies on the use of solar energy in various forms have been reported. Parabolic trough solar collectors are one of the most common ways to use solar thermal energy. Many investigations have been carried out on the study of various parameters of this system and their effect on the efficiency. In this study, a detailed numerical study on the impact of thermo-physical properties of the heat transfer fluid on the system efficiency have been performed and the fluid have been optimized. Parabolic trough solar collector is modelled by dividing the structure of the device into three layers:...
Geomechanical Model for Well Path Optimization Based on Inclination, Azimuth and ROP
, M.Sc. Thesis Sharif University of Technology ; Shad, Saeed (Supervisor)
Abstract
The wellbore instability increases the cost of drilling operations due to problems such as pipe sticking and lost circulation, so it is important to find the optimal well path. In this research, building a one-dimensional geomechanical model is investigated, and then the wellbore stability during drilling in different layers is evaluated. The geomechanical model is constructed using available data (well log data, mud logging unit data, and drilling reports) in a study reservoir and the optimal well path is determined by the appropriate inclination and azimuth using the geomechanical properties of the field and the stress regime, taking into account the wellbore stability and shear failure...
Investigation on Transport Phenomena in Porous Media with Multiphase Flow
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
Porous media have many applications including heat exchangers, single-phase flow and multi-phase flow packed beds and reactors with different flow patterns, aquifers, and oil and gas reservoirs. To evaluate the behavior of porous media there is need to understand transport phenomena. In this work, we focused on metal foam porous media as an advanced porous media. The effective thermal conductivity of solid matrix, heat transfer in the presence of fluid flow, and pressure drop were investigated using CFD techniques in micro-scale supposing that the solid foam structure consisted of connected kelvin cells. The comparison of simulation results with experimental data reported in literature shows...
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 ; Molaei, Asghar (Supervisor) ; Shahrokhi, Mohammad (Supervisor)
Abstract
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...
Heat Transfer and Pressure Drop Performance of Spiral Baffle Heat Exchangers
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Fathollah (Supervisor)
Abstract
In this work, a numerical investigation on shell side performance of a continuous helical baffle helixchanger along with smooth and helically ribbed tubes using CFD commercial code, Fluent, has been performed. The results of simulation for this type of exchanger were compared to a similar heat exchanger with segmental baffles. The geometries are created and meshed using Solidworks and Ansys Meshing softwares, respectively. Mesh generation is carried out using unstructured tetrahedral type elements. Element size (or number of elements) are chosen in such a manner that maintain accuracy and reliability of results in a reasonable run time. Simulation validation were carried out by comparison of...
Modeling and Simulation of Magnetic Nanofluids Convective Heat Transfer around a Sphere in the Presence of External Magnetic Feild
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
The good performance in cooling, especially in systems with small dimensions, is one of the critical needs of many industries. Heat transfer around sphere in all systems that contain particles, is important. Many methods have been proposed to improve the heat transfer rate but using nanofluids is one of the ways that has attracted more attention than others. Ferrofluids have magnetic properties in addition to nanofluids properties and this has a significant impact in increasing the heat transfer rate. Controlling heat transfer by magnetic field is one of the unique characteristics of this fluid. The project aim is to investigate the effect of magnetic field on heat transfer around sphere in...
Drug Delivery into the Anterior Segment of the Eye
, M.Sc. Thesis Sharif University of Technology ; Abdekhodaie, Mohammad Jafar (Supervisor) ; Bastani, Daruosh (Supervisor)
Abstract
Transport phenomena i.e. momentum, heat and mass transfer are occurring inside the eye constantly. Any disturbance in each of these could lead to diseases or ocular problems. Konwledge of transport phenomena can help surgeons and specialists to identify problems more easily and cure the problems effectively. Further more, these phenomena have a great impact on drug delivery inside the eye. Therefore deep understanding of them makes investigation of different therapies easy and convenient. Consequently this understanding could lead to choose the best method and route of administration available. A precise model which is in consistence with the real human eye has been developed and the ocular...