Search for: heat-transfer
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    Numerical Simulation of Nano-Impinging-Jet in Electronic Cooling Applications

    , M.Sc. Thesis Sharif University of Technology Akhlaghi, Hassan (Author) ; Darbandi, Masoud (Supervisor)
    With a fast progress in nanotechnology devices and components, e.g., MEMS/NEMS, heat transfer study in micro/nanoscales has become so critical for the systematic design and precise control of such miniaturized devices towards the integration and automation of Lab-on-a-chip devices. Demands in high heat transfer rates have returned the concerns to impinging jet cooling systems. However, studying impinging jets in the micro/nano scales is requires the molecular dynamics knowledge to analyze the true micro/nanoscale flow behavior accurately. According to the importance of this subject, we use direct simulation Monte Carlo (DSMC) method to simulate nano impinging jet gas flows. The thesis is... 

    Experimental of Convective Heat Transfer Coefficient Around a Vertical Rod Bundle

    , M.Sc. Thesis Sharif University of Technology Molla Bagher Makhmalbaf, Mohammad Hadi (Author) ; Jafari, Jalil (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)
    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... 

    Prediction of Homogeneos Charge Compression Ignition (HCCI) Engines Performance Using Multi-Zone Model

    , M.Sc. Thesis Sharif University of Technology Shahzadi, Hossein (Author) ; Mozafari, Ali Asghar (Supervisor)
    Some researches have been carried out in the last 20 years in order to increase the present IC engines thermal efficiency and their optimum performance. (HCCI) engine is viewed as a combination of spark-ignition (SI) and compression-ignition (CI) engines. This is because HCCI engines use premixed fuel/air mixture like SI engines and have auto ignition combustion after the mixture is compressed like CI engines. Control of combustion and ignition timing are the main challenges of these engines. Ignition delay, compression ratio, fuel air equivalence ratio and intake temperature and pressure are considered to be the most effective parameters on HCCI combustion.HCCI engines have great potentials... 

    Modeling, Analysis and Possible Solution for Excessive Intraocular Pressure in Glaucoma Patients

    , M.Sc. Thesis Sharif University of Technology Singh, Dara (Author) ; Firouzbakhsh, Keykhosrow (Supervisor)
    With the advent of new computer technologies, computational analysis on the human organs has become tremendously popular in the field of medical science. Every year thousands of people suffer irreversible eye damages pertaining to lack of adequate medications. In this regards, enormous amount of money is spent annually but mostly in vain due to the irreversibility and silent nature of eye diseases like glaucoma. Yet more precise studies on the topic are requisite. In this thesis, a validated half 3D finite volume model of human eye considering the fluid flow in collaboration with heat transfer in the steady state utilizing the well known discretized bio-heat transfer equation coupled with... 

    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)
    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... 

    Study of Mechanism of Formation of Metal Oxide Nanoparticles in Supercritical Water Medium

    , M.Sc. Thesis Sharif University of Technology Akhlaghpasand, Hamze (Author) ; Outokesh, Mohammad (Supervisor) ; Ahmadi, Javad (Co-Advisor)
    One of the most convenient methods for the synthesis of metal oxide nanoparticles, inorganic ceramic materials and catalysts is supercritical hydrothermal method. In its pure form or mixed metal oxide nanoparticles have potential applications are wide. An important aspect of functional metal oxides of uranium dioxide as the selective catalyst for the conversion of methane to methanol and chlorinated organic matter decomposition is used. The main issue that led to the definition of this project was that nanoparticles synthesized with supercritical hydrothermal conditions influenced by change in the temperature. Temperature also affects the particle size and the conversion efficiency. This... 

    , M.Sc. Thesis Sharif University of Technology Shokrani, Mohammad (Author) ; Dolati, Abolghasem (Supervisor)
    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... 

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

    , M.Sc. Thesis Sharif University of Technology Yarahmadi, Mehran (Author) ; Shafii, Mohammad Behshad (Supervisor)
    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 a magnetic field. Both constant magnetic field and alternating magnetic field was examined. Moreover magnetic field layout and strength and modes of alternating magnetic field was investigated. 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... 

    Numerical Solution of Flow and Heat Transfer in Micro Heat Pipes

    , M.Sc. Thesis Sharif University of Technology Mondegari, Ali (Author) ; Farhanieh, Bijan (Supervisor) ; Afshin, Hossein (Co-Advisor)
    One of the important issues that increasing development of electronic systems has caused is how to transfer the generated heat out of the system. Heat pipes can transfer large amount of heat because of using latent heat of evaporation and condensation. In micro scales using micro heat pipes is popular that in this instrument liquid returns to evaporator by means of surface tension force. So numerical solution is essential for verifying experimental results and increasing performance of this instrument. In this research has been planned to develop a comprehensive model for numerical solution of flow and heat transfer in micro heat pipes. For this reason surface evaporation and …,... 

    Multi-objective Optimization of Internal Cooling Passages for a Turbine Blade

    , M.Sc. Thesis Sharif University of Technology Bokaei, Hamid Reza (Author) ; Mazaheri, Karim (Supervisor)
    In the present work, the shape and position of internal cooling passages within an axial turbine blade have been optimized to achieve a uniform temperature distribution with the minimum cooling air flow while the maximum temperature is below the allowable value. Four cooling passages are made within the blade. The cross section shape of each passage is parameterized using a new method based on an 8-order Bezier curve. This curve which is represented in terms of Bezier control points has much flexibility and can produce a large variety of shapes. The shape of the blade surface profile remains unchanged during the optimization process. The numerical simulation has been carried out using... 

    Thermal Simulation of Sponge Iron Production by Höganäs Method

    , M.Sc. Thesis Sharif University of Technology Akbarian, Amir Hassan (Author) ; Halali, Mohammad (Supervisor)
    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... 

    Modeling of Phase Change Materials Operating in Energy Efficient Buildings

    , M.Sc. Thesis Sharif University of Technology Kayedpour, Kamran (Author) ; Saeedi, Mohammad Hassan (Supervisor) ; Zabihollah, Abolghasem (Co-Advisor)
    Shortage of energy sources in the new decade along with the increasing level of greenhouse gas emissions urges researchers in the field of energy to explore for the new source of energy as well as seeking for methods for usage of available energy resources more efficiently. Therefore, development of building with low level of energy usage may significantly reduce the need for grid energy. This can be met with new construction materials to reduce the energy consumption, using renewable energies sources such as solar and wind as well as design and development of materials with capability to store energy. The use of materials which can store energy and release it when needed has been considered... 

    Thermal Analysis of Regenerative Cooling in Liquid Rocket Engines

    , M.Sc. Thesis Sharif University of Technology Azizi, Mahdi (Author) ; Kebriaei, Azadeh (Supervisor)
    In this thesis to simulate the behavior of liquid engine Thrust chamber of hot gas from a quasi one dimensional code used when the effects of the heat transfer and friction in those terma. As well as during the regenerative channel is simulated by considering the equation’s of continuity, momentum and energy for one dimensional, effects of increase temperature, pressure drop, change the density of coolant flow resulting from the warming which is visible along the way to increase the accuracy of calculation of the thermal flux output of the engine, use a suitable model for unclear boiling in consideration of heat transfer coefficient used coolant flow it has been. As well as coupling of heat... 

    Development of Radiation Heat Transfer Modeling in Non-gray Media in Industrial Applications

    , M.Sc. Thesis Sharif University of Technology Barezban, Mohammad Bagher (Author) ; Darbandi, Masoud (Supervisor)
    Radiation evaluation in non-gray gaseous media is a very complicated issue. Previous researches have shown that the radiation properties of non-gray gases would strongly depend on the wavelengths. The gray gas assumption is the simplest model to calculate the radiation properties. Dispite simplicity, it is widely used in various industrial applications. In this model the gas radiation properties are assumed no to chang across all wavelengths. Evidently this would results in an inaccurate radiation modeling. Using the Spectral Line-based Weighted-sum-of-gray-gases model, SLW, the spectral behavior of radiation properties of gas is almost taken into account in computations. So the use of this... 

    Heat Transfer Enhancement in Shell-and-Tube Heat Exchangers Using Porous Media

    , M.Sc. Thesis Sharif University of Technology Esmaeili Rad, Sepideh (Author) ; Farhanieh, Bijan (Supervisor) ; Afshin, Hossein (Supervisor)
    Heat transfer enhancement in heat transfer equipment, such as heat exchangers, has been widely studied. There are plenty of techniques to increase heat transfer in tubular heat exchangers. One of these techniques is applying a porous medium. These media have a great interface with fluids which can enhance the heat transfer rate. Meanwhile, the thermal conductivity of these media is usually greater than that of the studied fluid. Thus, by adding a kind of highly conductive porous insert to a heat exchanger, we are able to save the material used to construct the device and the space occupied by it.
    Shell-and-tube heat exchangers are one of the most widely-used types of exchangers in... 

    Heat Transfer Modelling and Mechanical Properties Of Wide-Gap Thermite Rail Welds

    , Ph.D. Dissertation Sharif University of Technology Mohassel, Abbas (Author) ; Kokabi, Amir Hossain (Supervisor) ; Davami, Parviz (Supervisor)
    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... 

    Performance of Partially Filled Mini-Channels with Porous Media

    , M.Sc. Thesis Sharif University of Technology Azimi, Adel (Author) ; Nouri, Ali (Supervisor) ; Moosavi, Ali (Co-Advisor)
    Laminar forced convection flow through a channel partially filled with a porous material was numerically studied in this thesis. The Navier-Stokes and Brinkman-Forchheimer equations were used to model the fluid flow in the free and porous regions, respectively. Coupling of the pressure and velocity fields was resolved using the SIMPLEC algorithm. The local thermal equilibrium was adopted in the energy equation. The effects of the thermal conductivity ratio, Darcy number, porosity, Reynolds number and height of the porous insert on velocity and temperature field were investigated. The results show that the flow behavior and its associated heat transfer are susceptible to the variation of the... 

    Computational Simulation of Cooling of Porously Covered Surfaces, Using a Navier-stokes and Lattice Boltzmann Solver

    , Ph.D. Dissertation Sharif University of Technology Salimi, Mohammad Reza (Author) ; Tayyebi Rahni, Mohammad (Supervisor) ; Jam, Freydoon (Co-Advisor)
    Considering the wide range of applications of porous media for heat transfer enhancement in various components of industrial machineries, including solar collectors, air dryers, compact heat exchangers, electronic microchips, investigation of heat transfer characteristics in porous media has been a major concern for many researchers. On the other hand, precise understanding of the physics of porous media-flow interaction has been an open research topic for a long time. The present research however, has aimed at developing a computational method to simulate the interaction between fluid flow and porous media to investigate heat transfer from prously covered surfaces. Pore scale modeling of... 

    Visualization and Investigation of The Influence of the Connecting Channels on Flat-Plate Pulsating Heat-Pipes’ Heat-Transfer

    , M.Sc. Thesis Sharif University of Technology Ebrahimi Dehshali, Massoud (Author) ; Shafii, Mohammad Behshad (Supervisor)
    A desired circulatory flow in flat-plate pulsating heat-pipes may improve electronic thermal management. This desired flow can be achieved by fabricating connecting channels (CCs) to increase flow resistance in one direction. In addition, connecting channels may increase the freedom degree of fluid. In order to investigate the effect of CC, two aluminum flat plate thermal spreaders with overall size 320mm×220mm×5mm - one with CC (CC-FPHP) and one without it- were fabricated. Both of the speaders have square channels with crosssection 2mm×2.8mm. The FPHPs were charged with ethanol as working fluid with filling ratios of 35%, 50%, 65%, and 80% by volume. Performance of connecting-channels in... 

    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...