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heat-transfer
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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...
Review and Simulation Process of Deposition in Fluidize Bed(Focus on Heat Transfer)
, M.Sc. Thesis Sharif University of Technology ; Roosta Azad, Reza (Supervisor) ; Yaghmaei, Soheyla (Co-Advisor)
Abstract
This project related to gas purification according to difference in the deposition point in the fludized bed.The main reason for choosing fluidized bed is increasing overall heat transfer coefficient compare in to other heat exchangers. Separation process, by cooling the wall causes the self- deposition gas phase shifts to solid phase. Solid formed on the wall, act as an insulating layer and greatly reduces the heat transfer. To solve this problem, the fluidized bed system is offered because fluid particles in addition to remove the insulating layer, improving convection heat transfer coefficient . Laboratory tests show the feasibility of preventing the formation of insulating layer by...
Heat Transfer Coefficient Prediction in Shell and Tube Heat Exchanger with Twisted Tube Bundle by CFD
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Fathollah (Supervisor)
Abstract
In this thesis, shell and tube heat exchanger with twisted tube bundle in 5 different twist angles is investigated using CFD commercial software, Fluent. A three dimensional unstructured grid has been employed to simulate the heat exchanger model. Optimum grid size is selected according to the level of accuracy required, optimum run time and the available computational resources. The method and simulation accuracy were verified by comparing simulation result with data from Bell-Delaware method. The RNG-K-ϵ method and second order discretization scheme for all variables are selected to model turbulent flow and solve the governing equations. Overall Heat transfer coefficient and pressure drop...
A Model for Temperature Distribution Prediction of a Non-Newtonian Fluid in an Agitated Vessel by CFD Method
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Fathollah (Supervisor)
Abstract
In this thesis heat transfer coefficient and temperature distribution of two Non-Newtonian and a Newtonian fluids in stirred vessel are investigated using Computational Fluid Dynamic (CFD). This vessel is agitated with new impeller called MAXBLEND. Non-Newtonian fluids are aqueous solutions of carboxymethyl cellulose 1.5%w/w and xanthan gum 3% w/w and Newtonian fluid is glycerin. This vessel is simulated in laminar regime with Reynolds number less than 14. The results of simulation are compared with correlation proposed by Kawase et al. Furthermore as a new research for this impeller, the effects of vessel diameter and position of impeller in the vessel on heat transfer coefficient are...
Implementation and Analysis of Thermal Model of High Voltage Induction Motors
, M.Sc. Thesis Sharif University of Technology ; Oraee Mirzamani, Hashem (Supervisor)
Abstract
Today, various industries rely on high-power, high-voltage induction motors for diverse applications. Given the critical role these motors play, any reduction in their lifespan or occurrence of failures can lead to substantial financial losses and even pose risks to lives. One significant factor influencing motor life is the temperature of its components. Manufacturers strive to enhance motor power while minimizing dimensions for economic reasons, but this increases power density and subsequent losses, elevating motor temperature. Consequently, thermal analysis becomes crucial, posing a significant challenge for companies producing high-power induction motors. In this study, a thermal model...
The Effect of Interfaces on Heat Transport Mechanism of Y-Ba-Cu-O Thin Film Superconducting Bolometer
, Ph.D. Dissertation Sharif University of Technology ; Vesaghi, Mohammad Ali (Supervisor) ; Fardmanesh, Mahdi (Supervisor)
Abstract
In this thesis, we are focusing on the heat transport mechanism in one of the most applicable kinds of superconducting detectors called, YBa2Cu3O7-x (YBCO) transition-edge bolometer. The Time Domain Thermoreflectance (TDTR) method is described as a tool for investigating the thermal boundary conductance and thermal conductivity of the materials, and the measured thermal conductivity of our YBCO films is reported here. Although some recent papers have shown a dependence of the thermal conductivity of the YBCO films to their thickness, our results on many samples with different substrates didn’t show the reported thickness dependency and we have obtained the thermal conductivity of the YBCO...
Microstructure evolution and microhardness of friction stir welded cast aluminum bronze
, Article Journal of Materials Processing Technology ; Vol. 214, issue. 8 , August , 2014 , pp. 1524-1529 ; ISSN: 09240136 ; Kokabi, A. H ; Sharif University of Technology
Abstract
Microstructural characteristics and mechanical properties of a friction stir welded cast aluminum bronze (Cu-9Al-1Fe), produced by a sand casting method, have been investigated at tool rotation of 850-1500 rpm and traverse speed of 50-100 mm/min. Refinement of the primary coarse cast microstructure in the base metal was seen after friction stir welding. Microstructure of the stir zone was characterized in four distinct areas of non-isometric fine grains while a significant grain growth was noticed in some of the areas. Conditions of grain growth are defined with high heat input intensity and low heat transfer capability. The grain size was observed to decrease after FSW, resulting in a...
Analyses of mass and heat transport interactions in a direct methanol fuel cell
, Article International Journal of Hydrogen Energy ; Vol. 39, issue. 21 , July , 2014 , p. 11224-11240 ; ISSN: 03603199 ; Baghalha, M ; Sharif University of Technology
Abstract
In this paper, a two-dimensional, two-phase, non-isothermal model is presented to predict the electrochemical, mass transfer and heat transfer behaviors in a direct methanol fuel cell (DMFC). Governing equations including the momentum, continuity, heat transfer, proton and electron transport, species transport for water, methanol, and all the gas species (carbon dioxide, methanol vapor, water vapor, oxygen, and nitrogen) and the auxiliary equations are coupled to studying the various phenomena in DMFC. The modeling results agree well with the four different experimental data in an extensive range of operation conditions. A parametric study is also performed to examine the effects of the cell...
Heat transfer between micro- and nano-mechanical systems through optical channels
, Article Journal of the Optical Society of America B: Optical Physics ; Vol. 31, issue. 7 , 2014 , pp. 1525-1532 ; ISSN: 07403224 ; Bahrampour, A. R ; Sharif University of Technology
Abstract
In this paper, a new mechanism of heat transfer is introduced. It is shown that, without emission and absorption of photons, light can operate as a channel of heat transfer between nano- or micro-mechanical oscillators. We consider the dynamics of two vibrating mirrors coupled through one optical cavity mode in an optomechanical system. It is shown that light mediates heat transfer between two micro-mirrors. When the detuning frequency of the mechanical resonators is low, fluctuations flow through the light channel from the high temperature vibrating mirror toward the low temperature one. This behavior is named the resonance heat transfer effect. The rate of heat flow between the mechanical...
Comparison between Lagrangian and Eulerian approaches in predicting motion of micron-sized particles in laminar flows
, Article Atmospheric Environment ; Vol. 89, issue , 2014 , Pages 199-206 ; ISSN: 13522310 ; Rismanian, M ; Monjezi, M ; Zendehbad, M ; Fatehiboroujeni, S ; Sharif University of Technology
Abstract
Modeling the behavior of suspended particles in gaseous phase is important for diverse reasons; e.g. aerosol is usually the main subject of CFD simulations in clean rooms. Additionally, to determine the rate and sites of deposition of particles suspended in inhaled air, the motion of the particles should be predicted in lung airways. Meanwhile there are two basically different approaches to simulate the behavior of particles suspension, Lagrangian and Eulerian approaches. This study compares the results of these two approaches on simulating the same problem. An in-house particle tracking code was developed to simulate the motion of particles with Lagrangian approach. In order to simulate the...
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 ; 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...
Exergy analysis of a flat plate solar collector in combination with heat pipe
, Article International Journal of Environmental Research ; Vol. 8, Issue. 1 , 2014 , Pages 39-48 ; ISSN: 17356865 ; Shafii, M. B ; Rahni, M. T ; Abbaspour, M ; Sharif University of Technology
Abstract
The use of solar collectors in combination with heat pipes is rapidly growing in recent years. Heat pipes, as heat transfer components, have undeniable advantages in comparison with other alternatives. The most important advantage is their high rate of heat transfer at minor temperature differences. Although there have been numerous studies on the heat analysis or first thermodynamic analysis of flat plate solar collectors in combination with heat pipes, the exergy analysis of these collectors is needed to be investigated. In this work, energy and exergy analysis of a flat plate solar collector with a heat pipe is conducted theoretically. Next, the exergy efficiency of pulsating heat pipe...
The study of magnetic field implementation on cylinder quenched in boiling ferro-fluid
, Article Applied Thermal Engineering ; Volume 64, Issue 1-2 , March , 2014 , Pages 331-338 ; ISSN: 13594311 ; Saboonchi, A ; Shafii, M. B ; Jahani, N ; Sharif University of Technology
Abstract
It has been shown that nanofluids in different investigations increase or decrease heat transfer rate in boiling phenomenon. The present study examined the effects of ferro-fluid concentrations and magnetic field implementation on the fluid throughout the boiling process. Obtained are the quenching curve and boiling curve on specified surface roughness in both water and ferro-fluid with two different concentrations. A silver cylinder with Aspect ratio of 10, and surface roughness of 689 nm was heated up to 350 C and then was overwhelmed in the fluid under study. Temperatures were measured by a thermocouple which installed in the center of the cylinder. The test was carried out 5 times. The...
Empirical correlation for performance evaluation of electric/corona wind on natural convection
, Article Journal of Electrostatics ; Vol. 72, issue. 1 , February , 2014 , pp. 82-90 ; ISSN: 03043886 ; Shabahang-Nia, E ; Merdasi, A ; Sharif University of Technology
Abstract
The effect of the corona wind on the natural convection at a rectangular channel was investigated experimentally. The results indicate that the natural convection in the absence of electric/corona wind at obtuse angles outperforms than acute angles and keeps improving by increasing the angle. However, the efficiency of the electric/corona wind at acute angles is higher than obtuse angles. Generally, in the presence of electric/corona wind, heat transfer coefficient was increased. The effect of the electric/corona wind was decreased by raising heat flux. This mainly stems from the fact that the temperature gradient raises the thermal boundary layer and reduces the secondary flow power....
Open-loop pulsating heat pipes charged with magnetic nanofluids: powerful candidates for future electronic coolers
, Article Nanoscale and Microscale Thermophysical Engineering ; Volume 18, Issue 1 , 2014 , Pages 18-38 ; ISSN: 15567265 ; Taslimifar, M ; Haghayegh, S ; Hannani, S. K ; Shafii, M. B ; Saidi, M. H ; Afshin, H ; Sharif University of Technology
Abstract
The present research proposes an effective method to enhance the heat transport capability of conventional electronic coolers and improve their thermal management. Pulsating heat pipes (PHPs) are outstanding heat transfer devices in the field of electronic cooling. In the present study, two sets of open-loop pulsating heat pipes (OLPHPs) for two different magnetic nanofluids (with and without surfactant) were fabricated and their thermal performance was experimentally investigated. Effects of working fluid (water and two types of magnetic nanofluids), heating power, charging ratio, nanofluid concentration, inclination angle, application of a magnetic field, and magnet location are described....
Three dimensional heat transfer modeling of gas-solid flow in a pipe under various inclination angles
, Article Powder Technology ; Vol. 262, Issue. 1 , 2014 , pp. 223-232 ; ISSN: 0032-5910 ; Saffar Avval, M ; Mansoori, Z ; Amirkhosravi, M ; Sharif University of Technology
Abstract
The turbulent heat transfer in gas-solid flows through an inclined pipe under various inclination angles is studied with constant wall heat flux. The hydrodynamic k- τ and kθ- τθ thermal two phase model is used in a lagrangian/Eulerian four way approach. The numerical results agreed reasonably with available experimental data in vertical and horizontal pipe flows. The effects of inclination angles on the flow patterns are reported. The pressure drop and Nusselt number are enhanced significantly as the inclination increases up to a certain angle. The mass loading ratio has influence on the optimal inclination angle. With increasing loading ratio, the optimal inclination angle of maximum...
Effects of preheating temperature and cooling rate on two-step residual stress in thermal barrier coatings considering real roughness and porosity effect
, Article Ceramics International ; Vol. 40, Issue. 10 , December , 2014 , pp. 15925-15940 ; ISSN: 02728842 ; Farrahi, G. H ; Azadi, M ; Ghodrati, M ; Sharif University of Technology
Abstract
In this research, a finite element model was developed in order to simulate the two-step residual stress distribution of a thermal barrier coating system, considered to be used in diesel engine cylinder head, with a real roughness and real porosity. Two steps including the bond coat and the top coat deposition processes were taken into account. The real geometry of coating layers, including the roughness and the porosity, was also considered based on a scanning electron microscopy image. Then, effects of the convective heat transfer coefficient and initial substrate and substrate/bond coat preheating temperatures on the residual stress were studied. Obtained results illustrate that the...
CFD-aided simulation of frost growth inside a narrow duct with uniform wall temperature variation
, Article ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM 2014, Collocated with the ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting ; 2014 ; ISBN: 9780791846278 ; Asgari, E ; Hajikaram, M ; Schneider, G. E ; Sharif University of Technology
Abstract
In this paper, we study the frost formation and growth at the walls of a duct with uniform wall temperature variation. The simulation is performed for laminar flow regime considering suitable semi-empirical models incorporated with computational fluid dynamics (CFD) method. The frost growth is considered to be normal to the duct surface. Since the duct aspect ratio is high, we perform our simulations in two-dimensional zones. To simulate the frost layer properly, we solve both the energy and mass balance equations implementing some semi-empirical correlations on the frost side. At this stage, we suitably predict the required heat flux value at the solid boundary and the heat transfer...
Solving combined natural convection-radiation in participating media considering the compressibility effects
, Article 52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014 ; 13- 17 January , 2014 ; ISBN: 9781624102561 ; Abrar, B ; Schneider, G. E ; Sharif University of Technology
Abstract
In this work, we aim to study the effect of temperature gradients on the combined natural convection-radiation heat transfer problem in participating media. To impose this combined effect, we first solve the radiative transfer equation in an absorbing and emitting media. Then, we suitably add the radiation source terms to the energy equation and solve the fluid flow equations. Literature shows that many incompressible algorithms use the Boussinesq assumption to model the thermobuoyant force; however, the validity of this assumption is limited to cases with low temperature gradient distributions. Evidently, Boussinesq assumption would result in considerable errors in high temperature gradient...
Experimental characterization of stabilized suspensions caused by formation of nanoparticle halos
, Article ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM 2014, Collocated with the ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting ; 2014 ; ISBN: 9780791846278 ; Zabetian, M ; Saidi, M. H ; Mozafari, A. A ; Sharif University of Technology
Abstract
Suspension flow has an important role in various applications such as paint, material and pharmaceutical industries. Settling is considered as a resisting phenomenon in the processes dealing with suspensions. Using nanoparticles as an additive to micro-particulates has been studied in limited studies. This work presents an experimental investigation to assess the effectiveness of nanoparticles in reduction of suspension settling. Microscopic imaging and transmission measurement were used to analyze the stability factors in a container. Transmission analysis revealed that presence of nanoparticles in the suspension, decreased the sedimentation rate. Microscopy showed that the settling rate...