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Total 223 records

    Modelling the flow behaviour of steel under non-isothermal conditions

    , Article Materials Science and Technology ; Volume 19, Issue 8 , 2003 , Pages 1065-1069 ; 02670836 (ISSN) Serajzadeh, S ; Zebarjad, S. M ; Sharif University of Technology
    2003
    Abstract
    A mathematical model is proposed for evaluating flow behaviour under hot deformation conditions. The effects of dynamic recovery and recrystallisation as well as temperature and strain rate variations are considered in the model by means of Bergstrom's approach and the additivity rule for strain. To verify the model, hot compression tests for three grades of steel together with upsetting experiments are carried out. Comparison between experimental and theoretical results confirms the reliability of the model. © 2003 IoM Communications Ltd. Published by Maney for the Institute of Materials, Minerals and Mining  

    Theoretical modeling and optimizing design of a packaged liquid chiller

    , Article 2007 ASME/JSME Thermal Engineering Summer Heat Transfer Conference, HT 2007, Vancouver, BC, 8 July 2007 through 12 July 2007 ; July , 2007 , Pages 527-537 ; 0791842746 (ISBN); 9780791842744 (ISBN) Heydari, A ; Kargar, S ; Sharif University of Technology
    2007
    Abstract
    This work attempts to develop a physical simulation model for the purpose of studying the effect of various design parameters on the performance of a packaged liquid chiller. A computer model which simulates the steady-state cyclic performance of a vapor compression chiller is developed for the purpose of performing detailed physical design analysis of actual industrial chillers. The model can be used for optimizing design and for detailed energy efficiency analysis of packaged liquid chillers. The simulation model takes into account presence of all chiller components such as compressor, shell-and-tube condenser and evaporator heat exchangers, thermostatic expansion valve and connection... 

    Effect of inlet air cooling by absorption chiller on gas turbine and combined cycle performance

    , Article 2005 ASME International Mechanical Engineering Congress and Exposition, IMECE, Orlando, FL, 5 November 2005 through 11 November 2005 ; Volume 45 , 2005 , Pages 507-515 ; 10716947 (ISSN) Khaledi, H ; Zomorodian, R ; Ghofrani, M. B ; Sharif University of Technology
    2005
    Abstract
    Gas turbine performances are directly related to site conditions. The use of gas turbines in combined gas-steam power plants, also applied to cogeneration, increases such dependence. In recent years, inlet air cooling systems have been introduced to control air temperature at compressor inlet, resulting in an increase in plant power and efficiency. In this paper, the dependence of outside conditions for a simple gas turbine and a combined cycle plant is studied, using absorption chiller as inlet air cooling system. We used, as case study, a simple plant equipped with one frame E gas turbine and a combined cycle with a two pressure level heat recovery steam generator (HRSG). It was found that... 

    Fluid flow and heat transfer around circular cylinders in the presence and no-presence of porous media

    , Article Journal of Porous Media ; Volume 7, Issue 3 , 2004 , Pages 239-247 ; 1091028X (ISSN) Layeghi, M ; Nouri Borujerdi, A ; Sharif University of Technology
    2004
    Abstract
    Steady-state laminar and incompressible fluid flow and forced-convection heat transfer from a circular cylinder and an array of circular cylinders in the presence and no-presence of porous media are investigated. Various mathematical and numerical models are compared and the effects of porous media on heat transfer enhancement are studied. Navier-Stokes equations are used for the analysis of laminar fluid flow and heat transfer. However, the Darcy and extended Darcy-Brinkman models are used for the analysis of fluid flow and heat transfer in porous media. The cylinders are at constant temperature and the analysis is restricted to the low- and intermediate-Peclet-number regimes (Pr = 1, Re ≤... 

    Study of mixed-convection heat transfer from an impinging jet to a solid wall using a finite-element method - Application to cooktop modeling

    , Article Numerical Heat Transfer, Part B: Fundamentals ; Volume 46, Issue 4 , 2004 , Pages 387-397 ; 10407790 (ISSN) Karzar Jeddi, M ; Kazemzadeh Hannani, S ; Farhanieh, B ; Sharif University of Technology
    2004
    Abstract
    The mixed-convection flow from a hot vertical impinging jet on a colder horizontal disc has been studied. The geometry is analogous to a conventional burning gas cooktop. A numerical simulation of the system has been carried out using the finite-element method to study the dependence of fluid flow and heat transfer on the geometric, thermal, and fluid flow parameters. Results show that heat transfer efficiency versus several parameters such as inlet velocity magnitude and flue gas temperature has an optimum value, in which heat transfer efficiency is maximum. With thermal conductivity of the solid wall, velocity angle, and solid wall diameter heat transfer efficiency has increasing behavior.... 

    Transient and steady-state analysis of heat, mass, and momentum transfer in developing and fully-developed regions of homogeneous tubular reactors with non-Newtonian fluid flow

    , Article Energy Conversion and Management ; Volume 65 , 2013 , Pages 308-321 ; 01968904 (ISSN) Abbaszadeh Molaei, E ; Hashemi Amrei, S. M. H ; Molaei Dehkordi, A ; Haghi, M ; Sharif University of Technology
    2013
    Abstract
    In this article, the problem of simultaneous heat, mass, and momentum transfer in the developing region of tubular reactors with homogeneous chemical reaction and laminar power-law fluid flow under unsteady-state conditions has been solved. In this regard, the general governing equations were solved using finite-difference method and analyzed carefully. Moreover, the influences of various parameters and dimensionless numbers such as power-law index, heat of reaction, reaction order, and Damköhler number value on the numerical results were investigated. In addition, the numerical results obtained for the fully-developed velocity distribution of Newtonian fluid flow and Sherwood number value... 

    The characteristics of serrated flow in superalloy IN738LC

    , Article Materials Science and Engineering A ; Volume 486, Issue 1-2 , 2008 , Pages 376-380 ; 09215093 (ISSN) Sharghi Moshtaghin, R ; Asgari, S ; Sharif University of Technology
    2008
    Abstract
    Serrated flow was investigated in superalloy IN738LC, a nickel-base γ′ age-hardened alloy. In this material serrated flow appeared between 350 and 450 °C and strain rate of (8.77 × 10-5 to 8.77 × 10-3) s-1. Activation energy for this process was calculated to be 0.69-0.86 eV which is in good agreement with the values reported for similar alloys. Results show that the diffusion rate of substitutional solute atoms at this temperature range is too low to cause this effect. This suggests that the interaction of solute atoms and moving dislocation is responsible for the observed serrated flow in this alloy. © 2007 Elsevier B.V. All rights reserved  

    Numerical simulation of submerged flows with baffles uSING ν2̄ - F and k-ε turbulence models

    , Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 08888116 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) Mehdizadeh, A ; Firoozabadi, B ; Sherif, S. A ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2006
    Abstract
    This paper introduces the concept of a submerged hydraulic jump being used for energy dissipation. A baffle wall is used to produce a stable deflected surface jet, thereby deflecting the high-velocity supercritical stream away from the bed to the surface. An elliptic relaxation turbulence model (v 2̄ - f model) has been used to simulate this submerged flow. During the last few years, the v2̄ - f turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of damping functions. In addition, it has been proved that the v̄2 - f model is superior to other RANS methods in many fluid flows where complex flow features are present. In this study,... 

    Performance of valveless diffuser micropumps under harmonic piezoelectric actuation

    , Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) Ahmadian, M. T ; Saidi, M. H ; Mehrabian, A ; Bazargan, M ; Kenarsari, S. D ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Abstract
    Valveless piezoelectric micropumps are in wide practical use due to their ability to conduct particles with absence of interior moving mechanical parts. The objective of this paper is to obtain the fluid flow response to actuation frequency of a passive diffuser valve under harmonic pressures. In this regards a 2D model of a micropump valves and chambers is analyzed. The analysis is performed for 10Kpa back pressure on micropump chamber and actuation frequencies within the range of 1Hz to 10 KHz. Results show the highest velocity in the direction of diffuser axis occurs at the narrow diffuser neck while flow direction reverses every half period. For low frequencies, a parabolic velocity... 

    Design optimization of diffuser type valveless micropumps

    , Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) Saidi, M. H ; Mehrabian, A ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Abstract
    Valveless piezoelectric micropumps are in wide practical use due to their ability to conduct particles with absence of interior moving mechanical parts. In this paper, using finite element method, an extended numerical study on fluid flow through micropump chamber and diffuser valves is conducted to find out the optimum working conditions of micropump. In order to obtain maximum generality of the reported results, an analytical study along with a dimensional analysis is presented primarily, to investigate the main dimensionless groups of parameters affecting the micropump net flux. Consequently, the parameters appeared in the main dimensionless groups have been changed in order to understand... 

    Optimization of the pem fuel cell cooling system by entropy generation minimization

    , Article 3rd International Conference on Fuel Cell Science, Engineering, and Technology, 2005, Ypsilanti, MI, 23 May 2005 through 25 May 2005 ; 2005 , Pages 441-448 ; 0791837645 (ISBN); 9780791837641 (ISBN) Sharifian, L ; Saidi, M. H ; Sharif University of Technology
    American Society of Mechanical Engineers  2005
    Abstract
    Cooling system is essential for high power fuel cells to maintain cells temperature in an acceptable limit. In this paper a suitable cooling system for the PEM fuel cell has been designed and optimized. The design includes the number of the cooling plates, the proper circuit of the cooling channels in the plates, the channel dimensions, the flow rate of the cooling fluid and its temperature. The optimization technique is minimization of the entropy generation through the cooling plates. The design of the cooling channels and plates is such that the plate temperature doesn't exceed from a desired temperature and the temperature variation in the plate becomes minimized. In this design, the... 

    Modelling of foam degradation in lost foam casting process

    , Article Journal of Materials Science ; Volume 39, Issue 14 , 2004 , Pages 4593-4603 ; 00222461 (ISSN) Mirbagheri, S. H. M ; Silk, J. R ; Davami, P ; Sharif University of Technology
    2004
    Abstract
    In this investigation a new model was developed to calculate gas pressure at the melt/foam interface (Gap) resulting from foam degradation during mould filling in the lost foam casting (LFC) process. Different aspects of the process, such as foam degradation, gas elimination, transient mass, heat transfer, and permeability of the refractory coating were incorporated into this model. A computational fluid dynamic (CFD) code was developed based on the numerical technique of the Solution Algorithm-Volume of Fluid (SOLA-VOF) utilizing model, for the simulation and prediction of the fluid flow in the LFC process. In order to verify the computational results of the simulation, a thin plate of grey... 

    SPH simulation of interacting solid bodies suspended in a shear flow of an Oldroyd-B fluid

    , Article Journal of Non-Newtonian Fluid Mechanics ; Volume 166, Issue 21-22 , November , 2011 , Pages 1239-1252 ; 03770257 (ISSN) Hashemi, M. R ; Fatehi, R ; Manzari, M. T ; Sharif University of Technology
    2011
    Abstract
    An explicit weakly compressible SPH method is introduced to study movement of suspended solid bodies in Oldroyd-B fluid flows. The proposed formulation does not need further stabilizing treatments and can be efficiently employed to study particulate flows with Deborah to Reynolds number ratios up to around 10. A modified boundary treatment technique is also presented which helps to deal with the movement of solid particles in the flow. The technique is computationally efficient and gives an improved evaluation of fluid-solid interaction forces.A number of test cases are solved to show performance of the proposed method in simulating particulate viscoelastic flows containing circular and... 

    A reduced domain strategy for local mesh movement application in unstructured grids

    , Article Applied Numerical Mathematics ; Volume 61, Issue 9 , 2011 , Pages 1001-1016 ; 01689274 (ISSN) Darbandi, M ; Fouladi, N ; Sharif University of Technology
    Abstract
    Automatic control of mesh movement is mandatory in many fluid flow and fluid-solid interaction problems. This paper presents a new strategy, called reduced domain strategy (RDS), which enhances the efficiency of node connectivity-based mesh movement methods and moves the unstructured grid locally and effectively. The strategy dramatically reduces the grid computations by dividing the unstructured grid into two active and inactive zones. After any local boundary movement, the grid movement is performed only within the active zone. To enhance the efficiency of our strategy, we also develop an automatic mesh partitioning scheme. This scheme benefits from a new quasi-structured mesh data... 

    Numerical modeling of ureagenesis in a microfluidic channel mimicking a liver lobule

    , Article 2015 22nd Iranian Conference on Biomedical Engineering, ICBME 2015, 25 November 2015 through 28 November 2015 ; 2015 , Pages 54-59 ; 9781467393515 (ISBN) Sharifi, F ; Firoozabadi, B ; Saidi, M. S ; Firoozbakhsh, K ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    Ammonia detoxification is one of the main functions of the liver results in production of urea. In this study ammonia elimination and urea production was simulated in a microchannel mimicking the hepatic porto central axis. Navier- Stockes equations along with convection equations were solved for the related species in the entire domain. Since the Reynolds number was small (~1) the fluid flow regime was laminar. Urea cycle was modeled regarding its four main enzymes. Twelve rate equations were also solved in order to obtain the concentration of each metabolites participating in urea cycle. Concentration of the urea reached its maximum ca. 1.2e-5 M at the end of the channel which is in good... 

    An X-FEM implementation of hydro-fracture growth in naturally fractured saturated porous media

    , Article Poromechanics 2017 - Proceedings of the 6th Biot Conference on Poromechanics, 9 July 2017 through 13 July 2017 ; 2017 , Pages 2027-2034 ; 9780784480779 (ISBN) Vahab, M ; Khoei, A. R ; Khalili, N ; Sharif University of Technology
    Abstract
    In this paper, a coupled hydro-mechanical formulation is developed for the simulation of interaction between hydraulic fractures and natural discontinuities within saturated porous media. The momentum balance equation of the bulk together with the momentum balance and continuity equations of the fluid phase are employed to obtain the fully coupled set of governing equations. The hydro-fracture is modeled for fluid flow using the Darcy law. The natural discontinuity on the other hand is modeled for both opening and closing modes which induce fluid flow and/or contact behavior along the crack edges. The discontinuity in the displacement field is incorporated by using the Heaviside enrichment... 

    Soap-film flow induced by electric fields in asymmetric frames

    , Article Physical Review E ; Volume 97, Issue 4 , 2018 ; 24700045 (ISSN) Mollaei, S ; Nasiri, M ; Soltanmohammadi, N ; Shirsavar, R ; Ramos, A ; Amjadi, A ; Sharif University of Technology
    American Physical Society  2018
    Abstract
    Net fluid flow of soap films induced by (ac or dc) electric fields in asymmetric frames is presented. Previous experiments of controllable soap film flow required the simultaneous use of an electrical current passing through the film and an external electric field or the use of nonuniform ac electric fields. Here a single voltage difference generates both the electrical current going through the film and the electric field that actuates on the charge induced on the film. The film is set into global motion due to the broken symmetry that appears by the use of asymmetric frames. If symmetric frames are used, the film flow is not steady but time dependent and irregular. Finally, we study... 

    Recommendations on enhancing the efficiency of algebraic multigrid preconditioned GMRES in solving coupled fluid flow equations

    , Article Numerical Heat Transfer, Part B: Fundamentals ; Volume 55, Issue 3 , 2009 , Pages 232-256 ; 10407790 (ISSN) Vakili, S ; Darbandi, M ; Sharif University of Technology
    2009
    Abstract
    The algebraic multigrid (AMG) algorithm as a preconditioner to the Krylov subspace methods has drawn the attention of many researchers in solving fluid flow and heat transfer problems. However, the efficient employment of this solver needs experience, because users have to quantify several important parameters. In this work, we choose a hybrid finite-volume element method and quantify the optimum magnitudes for those parameters. To generalize our results, two sets of fluid flow governing equations, the thermobuoyant flow and confined diffusion flame, are studied and the optimum values are determined. The results indicate that the AMG can be very effective if a proper storage method is chosen... 

    Using nucleators to control freckles in unidirectional solidification

    , Article Experimental Thermal and Fluid Science ; Volume 33, Issue 8 , 2009 , Pages 1209-1215 ; 08941777 (ISSN) Shafii, M. B ; Alavi Dehkordi, E ; Esmaily Moghadam, M ; Mohseni Koochesfahani, M ; Sharif University of Technology
    2009
    Abstract
    Buoyancy-induced fluid flow, which is responsible for most forms of macro-segregation and channel-type segregates in castings, is not directly controllable. If left uncontrolled, natural convection will contribute to non-uniform distribution of alloy constituents and grain structure during solidification of a casting. Non-uniform distribution of chemical composition and physical structure in an alloy casting can significantly affect the reliability of mechanical components. Therefore, materials with acceptable defects can be produced only by trial-and-error and their acceptability is determined by costly inspections. We present a novel technique to control the formation of chimneys and... 

    Numerical modeling of die filling of semi-solid A356 aluminum alloy

    , Article Semi-Solid Processing of Alloys and Composites 10 - Selected, peer reviewed papers from the 10th International Conference on Semi-Solid Processing of Alloy and Composites, S2P 2008, Aachen, 16 September 2008 through 18 September 2008 ; Volume 141-143 , 2008 , Pages 605-610 ; 10120394 (ISSN); 9771012039401 (ISBN) Foroughi, A ; Aashuri, H ; Narimannezhad, A ; Khosravani, A ; Kiani, M ; Sharif University of Technology
    Trans Tech Publications Ltd  2008
    Abstract
    Computer base and simulation technique have been applied for modeling the semi-solid die filling and part of the solidification process of aluminum A356 alloy. A fairly simple one-phase rheological model has been implemented into a fluid flow finite element software Procast, to solve the partial differential equations. This model is purely viscous nature and is implemented in the power law cut-off model of Procast. The constitutive parameters of this model were determined for a rheocast A356 alloy. Using these parameters and comparing the simulation results with experimental data showed good correlation with the model prediction. The designed die for rheocasting was applied for the...