Loading...
Search for:
heat-transfer
0.019 seconds
Total 636 records
Rolling Contact Mechanics of Graded Coatings Involving Frictional Heating
, Ph.D. Dissertation Sharif University of Technology ; Adibnazari, Saeed (Supervisor) ; Karimzadeh, Ardavan (Co-Supervisor)
Abstract
In this Thesis ,the two-dimensional thermoelastic tractive rolling contact problem for an FGM coated half-plane under the plane strain deformation is investigated. A rigid cylinder rolls on the surface of an FGM coated half-plane with constant translational velocity, generating frictional heat in the slip zones of the contact area. Thermo-mechanical properties of the FGM vary exponentially along the thickness. It is assumed that the contact area consists of a central stick zone and two slip zones of the same sign. The transfer matrix method and Fourier integral transform technique are used to achieve a system of two Cauchy singular integral equations. The associated governing equations are...
Dynamics and Heat transfer of Two-phase Non-Newtonian Fluids in Superhydrophobic Channels
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
When the fluid passes through the microchannel, some energy is lost due to drag force and pressure drop. One of the methods used in the last few decades to optimize energy consumption is creating superhydrophobic surfaces in microchannels. These surfaces, with their features such as increasing the contact angle and reducing the contact angle hysteresis, can reduce energy loss, which is due to the presence of unevenness on the surface, and by trapping air and creating a two-phase flow, they reduce the drag force. On the other hand, the air trapped inside these irregularities will also affect the heat transfer of the passing fluid in the microchannel, which by creating resistance in the...
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...
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,...
Numerical Solution of Flow and Heat Transfer in Micro Heat Pipes
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor) ; Afshin, Hossein (Co-Advisor)
Abstract
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 …,...
Numerical Solution Of One-Dimensional Non-Fourier Bioheat Transfer Through Skin Tissue
, M.Sc. Thesis Sharif University of Technology ; Taghizadeh Manzari, Mehrdad (Supervisor)
Abstract
Innovations in laser, microwaves, and similar technologies have significantly advanced thermal treatments for diseases or even injuries concerning skin tissue. For a thorough understanding in the underlying mechanisms of bioheat transfer behavior of skin,a1D unsteady non-dimensional hyperbolic model of heat transfer through this tissue with metabolic heat generation which is subject to specific boundary conditions, is solved numerically using the finite difference method. A thermal shock is generated at the base of the tissue, which moves forward with a finite speed. A Numerical solution for a simple one-layer skin tissue is obtained. Then, the effects of various parameters, time step,...
Tomography with Inverse Heat Transfer
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor)
Abstract
Tomography offers a unique opportunity to unravel the complexities of the internal structure of an object without the need to invade it. There are various methods for this reason, in which all of them occupy wave or energy,ffiduction for imaging inside an object. Since the tomography plays a vital role in medicine and industry and present methods have limitation and difficulties to operate, the necessity for developing it has been inevitable. In this thesis a new tomography method has been presented in which uses inverse heat conduction for estimating unknown object with heat conductivity k2 inside a known domain with heat conductivity k 1 • For this purpose temperature is measured at...
Development of a Suitable Computational Conjugate Heat Transfer Algorithm to Analyze Turbine Blade Internal Cooling
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
Nowadays, the study of flow and heat transfer in turbine engines has become critical due to their increasing use and importance in various engineering industries. The critical issue of blade burning in the first row of turbine’s blades illuminates the critical roles of numerical and experimental activities in reducing these undesirable effects. Since blade cooling is directly related to the secondary air system, one important issue in blade burning research is to utilize the conjugate heat transfer approach. As Known, an increase of about 1% in the mass flow of air entering into the secondary air system would cause an increase of about 0.5% in the engine specific fuel consumption (SFC),...
A Numerical Model Development for Cryogenic Spiral Wound Heat Exchanger Design Considering Temperature dependent thermo-physical properties, Heat Leakage, and Longitudinal Heat Conduction
, M.Sc. Thesis Sharif University of Technology ; Afshin, Hossein (Supervisor)
Abstract
Cryogenic temperature is below than 123 Kelvin and any physical study that occurs below this temperature is Cryogenic science. Cryogenic has varaiety of application in medical, industry, food, oil and gas etc. Based on this paper and its relavant source spiral wound HE is one of the most optimum HE for cryogenic application specially for helium liquification cycle. In order to liquefy helium in helium cycle efficiency of spiral wound HE shall be over than 85 percent. For this reason and special fluid behavour in low temperature considering property variation, heat in leak and axial conduction is vital for calculating efficiency in cryogenic temperature of helium liquification cycle. In this...
Development of Radiation Heat Transfer Modeling in Non-gray Media in Industrial Applications
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
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...
Development of Finite Volume Method for Coupled Radiative, Convective, and Conductive Heat Transfer in Participating Media
, Ph.D. Dissertation Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
Numerical simulations of participating media need careful solution of the radiation transfer equation (RTE) along the fluid flow governing equations. Evidently, the accuracy of achieved solutions highly depends on the accuracy of radiation transfer calculations. Despite numerous efforts performed in the previous researches, the RTE calculation still faces with several challenges from both accuracy and computational cost perspectives. The main objective of this research is to present new contributions in overcoming such challenges. So, a finite-volume (FV) solver is suitably developed to solve the RTE numerically. This extended solver is then coupled with an existing FV flow solver. The...
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 ; Sattari, Sorena (Supervisor) ; Rashidi, Alimorad (Co-Advisor)
Abstract
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...
Analysis of Thermoelastic Damping in Microbeams and Microplates Based on the Non-Classical Continuum Mechanics and Heat Conduction Theories
, Ph.D. Dissertation Sharif University of Technology ; Asghari, Mohsen (Supervisor)
Abstract
Due to the features like small dimensions, low manufacturing cost and low power consumption, micro-electromechanical systems (MEMS) are widely utilized in engineering applications. Many experimental investigations have indicated that the mechanical behavior of constructive microelements of these systems isn’t predictable by classical continuum theory. Therefore, to analyze the behavior of microelements, the non-classical continuum theories which can capture size effects should be utilized. On the other hand, various experimental observations have confirmed that thermoelastic damping (TED) is a dominant source of energy dissipation in microelements, in contrast to the non-small parts and...
Thermal and Hydrodynamic Analyses of Shell and Tube Heat Exchangers in Different Flow Regimes Using Semi-Full-Scale Simulation Approaches
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
One main problem in many numerical simulations is the lack of sufficient infrastructure data to precisely model and analyze the flow through complex geometries. Since experimental procedures are generally very expensive; and sometimes impossible, it becomes necessary to find alternative ways such as numerical approaches to predict the flow behavior through complex geometries. The heat exchangers can be categorized as geometries with complex configuration and apparently expensive to solve numerically. They are widely used in different industries including the aerospace. The restrictions in design and implementation of aviation’s heat exchangers have promoted the related companies to converge...
Thermal Analysis of Regenerative Cooling in Liquid Rocket Engines
, M.Sc. Thesis Sharif University of Technology ; Kebriaei, Azadeh (Supervisor)
Abstract
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...
Thermal Analysis of Tiba Engine Cylinder Head
, M.Sc. Thesis Sharif University of Technology ; Afshin, Hossein (Supervisor) ; Hosseini, Vahid (Supervisor)
Abstract
These days, the heat transfer phenomena is an important issue in internal combustion engines design because of direct effects on the performance, efficiency and emission of engine. One of the main parts is cylinder head which contacts with hot gases in combustion chamber and expose high heat flux. In this thesis, cylinder head of Tiba engine modeled by three dimensional and transient thermal analysis. In this modeling in order to consideration the effect of fluid flow, different domain of cylinder head (water jacket, intake/exhaust ports) has been simulated and appended to the model. Also combustion phenomena modeled separately, and then the heat transfer coefficient in the surface of...
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...
Effect of tiO_2 Nanoparticles on Heat and Drag Properties of Dilute Polymer Solutions
, M.Sc. Thesis Sharif University of Technology ; Ramezani Saadat Abadi, Ahmad (Supervisor) ; Mohammadi, Mohammad Reza ($item.subfieldsMap.e)
Abstract
In the present work, the experiments were carried out for two types of PAM (3330 and 3630) with three distinct concentrations (25, 40 and 55 ppm) and TiO_2-water nanofluid for four concentrations (1.5, 2, 2.5 and 3 vol. %), and the Nusselt number and friction factor for each of them expressed separately. The Reynolds number was in the range from 11000 to 21000. The steady state turbulent convective heat transfer and friction factor of the combination of TiO_2-water nanofluid and polymer 3330 in the coiled tube were investigated. The effects of the Reynolds number for 2 vol. % nanoparticles which consists of 25 ppm PAM (3330) determined at the constant temperature of 24°C. It was observed...
Effect of Blade fin on Pressure Drop and Heat Transfer in Microchannels
, M.Sc. Thesis Sharif University of Technology ; Nouri Borujerdi, Ali (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)
Abstract
Nowadays, the cooling of electronic equipment has become a challenge for designers and scientists due to their progress. One of the most effective solutions for cooling these devices is using microchannel heat sinks. Researchers conducted so many studies experimentally, numerically, or a combination of them to increase the efficiency of microchannel heat sinks. Several methods have been proposed in previous studies to improve the cooling performance, such as using fins, nanoparticles, porous material, etc. Although increasing the heat exchange surface by using fins is caused to increase heat transfer, it also causes an increase in pressure drop. For this reason, researchers are looking for...
Multi-objective Optimization of Internal Cooling Passages for a Turbine Blade
, M.Sc. Thesis Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
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...