Search for: saidi--m--h
Total 219 records
Lattice Boltzmann simulation of TiO2-water nanofluid in a curved boundary domain at high Rayleigh numbers, Article Computers and Fluids ; Volume 168 , 30 May , 2018 , Pages 159-169 ; 00457930 (ISSN) ; Saidi, M. H
Elsevier Ltd 2018
In this paper, a two-component Lattice Boltzmann Method (LBM) has been utilized to simulate the natural convection of TiO2-water nanofluid in a curved geometry. The main purpose of this research is to study the effect of nanoparticle size and also boundary conditions on the thermal characteristics of the nanofluid. Furthermore, the effect of Rayleigh number (Ra) and volume fraction of nanoparticles (ϕ) on the average Nusselt number (Nuave) have been investigated. Two different thermal boundary conditions, namely adiabatic and constant temperature, have been considered in the current work for the curved boundaries. The Rayleigh number varies from 103 to 109. Four different sizes, namely 10,...
Article International Journal of Fluid Mechanics Research ; Volume 40, Issue 4 , 2013 , Pages 324-343 ; 10642277 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Flow hydrodynamics of laminar falling film of aqueous Li Br solution (Li Br - H2O) on a horizontal elliptical tube has been investigated in this research. The film velocity distribution and film thickness, namely, the flow characteristics are determined by solving analytically simultaneous simplified Navier - Stokes equations and continuity equation in polar and Cartesian coordinates. The analysis is based on steady state laminar flow of falling liquid film of Li Br - H2O on a horizontal elliptical tube in polar model and Cartesian model (CM), for cases in which traction on the film surface is considered negligible. Models are compared with each other in three cases of aspect ratios (Ar),...
Article Scientia Iranica ; Volume 19, Issue 3 , June , 2012 , Pages 431-436 ; 10263098 (ISSN) ; Saidi, M. H ; Sharif University of Technology
In the past two decades, microfluidic systems have become more appealing due to their wide applications in many areas, such as electronics, biotechnology, medicine, etc. Recently, the advantages of using the bubble growth phenomenon as a robust actuator in microfluidic devices have directed research interests towards the investigation of various applications. In this research, a new transient thermo-hydraulic model has been developed for bubble growth in confined volumes. The present model has been used to describe the pumping effect produced by the bubble growth and collapse phenomenon in microchannels. The results show relatively good agreement with experimental data. This study is useful...
Article Nanoscale and Microscale Thermophysical Engineering ; Volume 14, Issue 4 , 2010 , Pages 209-228 ; 15567265 (ISSN) ; Saidi, M. H ; Sharif University of Technology
In the present work, the second law of thermodynamics analysis has been carried out for steady-state fully developed laminar gas flow in a parallel plate microchannel with asymmetrically heated walls. The rarefaction effects as well as viscous heating effects are taken into consideration. Closed-form expressions are obtained for velocity and temperature distributions and entropy generation rates. The results demonstrate that increasing values of the wall heat fluxes ratio result in greater entropy generation for positive Brinkman numbers, whereas the opposite is true for negative values of Brinkman. However, the effect of the wall heat fluxes ratio on entropy generation becomes insignificant...
Viscous dissipation effects on thermal transport characteristics of combined pressure and electroosmotically driven flow in microchannels, Article International Journal of Heat and Mass Transfer ; Volume 53, Issue 19-20 , 2010 , Pages 3782-3791 ; 00179310 (ISSN) ; Saidi, M. H ; Sharif University of Technology
This study investigates the influence of viscous dissipation on thermal transport characteristics of the fully developed combined pressure and electroosmotically driven flow in parallel plate microchannels subject to uniform wall heat flux. Closed form expressions are obtained for the transverse distributions of electrical potential, velocity and temperature and also for Nusselt number. From the results it is realized that the Brinkman number has a significant effect on Nusselt number. Generally speaking, to increase Brinkman number is to decrease Nusselt number. Although the magnitude of Joule heating can affect Brinkman number dependency of Nusselt number, however the general trend remains...
Article Journal of Heat Transfer ; Volume 132, Issue 7 , 2010 , Pages 1-12 ; 00221481 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Fluid flow in microchannels has some characteristics, which one of them is rarefaction effect related with gas flow. In the present work, hydrodynamically and thermally fully developed laminar forced convection heat transfer of a rarefied gas flow in two microgeometries is studied, namely, microannulus and parallel plate microchannel. The rarefaction effects are taken into consideration using first-order slip velocity and temperature jump boundary conditions. Viscous heating is also included for either the wall heating or the wall cooling case. Closed form expressions are obtained for dimensionless temperature distribution and Nusselt number. The results demonstrate that for both geometries,...
Heat transfer and energy analysis of a pusher type reheating furnace using Oxygen enhanced air for combustion, Article Journal of Iron and Steel Research International ; Volume 17, Issue 4 , 2010 , Pages 12-17 ; 1006706X (ISSN) ; Saidi, M. H ; Sharif University of Technology
Oxy-fuel firing is more energy efficient and environmental friendly than conventional air-fuel firing and its application to reheating furnaces has hegun since 1990s. A computational method was presented to predict the steady heat transfer to the billets and temperature distribution in a continuous pusher type reheating furnace in which combustion air was enhanced by oxygen. Radiation heat flux calculated from the radiation heat exchange within the furnace was modeled using the FVM considering the effects of furnace walls and billets. Energy consumption per ton of steel, production rate and thermal efficiency of furnace, and trend of NOx emission in various levels of oxygen enrichment were...
Article Journal of Mechanical Science and Technology ; Volume 23, Issue 12 , 2010 , Pages 3448-3458 ; 1738494X (ISSN) ; Saidi, M.H ; Sharif University of Technology
Microchannels are at the forefront of today's cooling technologies. They are widely being considered for cooling of electronic devices and in micro heat exchanger systems due to their ease of manufacture. One issue which arises in the use of microchannels is related to the small length scale of the channel or channel cross-section. In this work, the maximum heat transfer and the optimum geometry for a given pressure loss have been calculated for forced convective heat transfer in microchannels of various cross-section having finite volume for laminar flow conditions. Solutions are presented for 10 different channel cross sections: parallel plate channel, circular duct, rectangular channel,...
Experimental investigation of drag and lift forces on microparticles in low reynolds number poiseuille flow in microchannel, Article Journal of Dispersion Science and Technology ; Volume 37, Issue 12 , 2016 , Pages 1767-1777 ; 01932691 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Taylor and Francis Inc
In this paper, the hydrodynamic drag and lift forces on microparticles in a dilute suspension in low Reynolds number Poiseuille flow in a microchannel is experimentally investigated using microscopic image analysis. An effective technique is applied to manipulate single-particle tracking in order to determine the velocity field and hydrodynamic forces on microparticles with diameter-to-channel height ratio of 0.1 (Formula presented.) in microchannels. The results show that there is a distance near the walls of the channel in which the hydrodynamic coupling between the particles and channel walls is considerable. Also, the magnitude of drag force that is imposed on the particles with...
Mass transport analysis of non-Newtonian fluids under combined electroosmotically and pressure driven flow in rectangular microreactors, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 508 , 2016 , Pages 345-359 ; 09277757 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Hydrodynamically fully developed flow of power-law fluids under combined action of electroosmotic and pressure gradient forces in rectangular microreactors is analyzed considering heterogeneous catalytic reactions. The Poisson-Boltzmann, Cauchy momentum, and concentration equations are considered in two dimensions and after being dimensionless are numerically solved applying a finite difference algorithm. Variation of axial concentration gradient, and axial and horizontal mass diffusions are taken into account as well. To accomplish a more general analysis, the velocity distribution is obtained by solving continuity and Cauchy momentum equations and is not considered as an average axial...
Simulation of natural convection of nanofluids at high rayleigh numbers: A two-component lattice Boltzmann study, Article Computational Thermal Sciences ; Volume 8, Issue 1 , 2016 , Pages 31-47 ; 19402503 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Begell House Inc
In this research, the effect of using nanoparticles on the Nusselt number in the natural convection at high Rayleigh numbers has been investigated. A two-component multiple relaxation times lattice Boltzmann code has been developed to investigate the natural convection of nanofluids in a 2D square enclosure. Three main forces, namely, buoyancy, drag, and Brownian forces are included to consider the interactions of the components. The potential force is also added to the model for the interactions among nanoparticles. The effects of Ra number, volume fraction of nanoparticles (ϕ), and size of nanoparticles (λ) have been investigated for two nanofluids (CuO-water and TiO2-water). Five...
Transportation and Settling Distribution of Microparticles in Low-Reynolds-Number Poiseuille Flow in Microchannel, Article Journal of Dispersion Science and Technology ; Volume 37, Issue 4 , 2016 , Pages 582-594 ; 01932691 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Taylor and Francis Inc
In this article, velocity field and settling distribution of microparticles in a dilute suspension in low-Reynolds-number Poiseuille flow in a microchannel is experimentally investigated using microscopic image analysis. An effective technique is applied to manipulate single-particle tracking in order to determine the controlling parameters on transportation and settling of microparticles in microchannels. The results show that the velocities of dispersed phase are affected by the hydrodynamic properties, and this velocity deviation can be significant when the hydrodynamic coupling between particles and channel walls is considerable. Increasing the Reynolds number would result in decrease in...
Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 53, Issue 9 , 2017 , Pages 2841-2851 ; 09477411 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Design and fabrication of solar collectors with high performance of energy efficiency to convert solar energy to utility energy is vitally important. This article reports the results obtained from design, construction and investigation of the performance of a Combined Multi-Purpose Vacuum Solar Collector (CMPVSC). This collector consists of three sections: the vacuum section, the liquid section and the air section. In the present collector, it is capable of transferring heat to two flows (liquid and air) simultaneously and separate with the possibility of multipurpose applications. The CMPVSC is compared with the existing individual collectors and the effects of different parameters on the...
Article Journal of Thermal Engineering ; Volume 3, Issue 1 , 2017 , Pages 1052-1059 ; 21487847 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Yildiz Technical University 2017
Solar heat energy, one of the typical renewable energy absorbs radiation energy from the sun and converts it into heat energy. Since it is sustainable and eco-friendly, it can be a good alternative to solve the problem of the depletion of fossil fuels. But it has low density. So, solar collector is very important to use more efficiently. There are some possible approaches to scaling-up the effectiveness of a collector by re-thinking of using the collector as a heat exchanger. In the design of dual-purpose collector with rectangular fin (DPCRF), can be used for heating air and water simultaneously using incident solar radiation resulting in optimum usage of energy and space
Numerical study of hydrogen-air combustion characteristics in a novel micro-thermophotovoltaic power generator, Article Applied Energy ; Volume 199 , 2017 , Pages 382-399 ; 03062619 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Elsevier Ltd 2017
In the present work, a micro combustor for thermophotovoltaic (TPV) devices is proposed which is included a U-shaped microtube in a box with a secondary fluid in space between U-shaped microtube and box walls. By utilizing the three-dimensional CFD model, combustion characteristics of the premixed lean hydrogen-air mixture in the present micro combustor are studied numerically with detailed chemistry and transport taking into account heat transfer through the wall. The results show that the establishment of secondary flows and better preheating in the curved tubes is caused the flammability limits to be at least four times in comparison with straight tubes. Combustion characteristics are...
The role of ion partitioning in electrohydrodynamic characteristics of soft nanofluidics: Inclusion of EDL overlap and steric effects, Article Chemical Engineering Science ; Volume 190 , 2018 , Pages 443-458 ; 00092509 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Elsevier Ltd 2018
In this paper, we aim to account for the partitioning of finite sized ions and electric double layer (EDL) overlapping effects on the electrostatics and hydrodynamics of soft nanofluidics by stablishing a modified Poisson-Boltzmann (MPB) equation enjoying mean field approach. The application of the present MPB equation enables us to describe the interaction between the steric effect and electrostatic repulsion of EDL ions due to permittivity difference of polyelectrolyte layer (PEL) and electrolyte solution. Utilizing the Debye-Hückel approximation pertinent to low surface potentials, we analytically derive the solutions of electric potential and velocity profiles of mixed electroosmotic and...
3D investigation of natural convection of nanofluids in a curved boundary enclosure applying lattice Boltzmann method, Article International Journal of Numerical Methods for Heat and Fluid Flow ; Volume 28, Issue 8 , 2018 , Pages 1827-1844 ; 09615539 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Emerald Group Publishing Ltd 2018
Purpose: The purpose of this paper is to investigate the natural convection behavior of nanofluids in an enclosure. The enclosure is a 3D capsule with curved boundaries filled with TiO2-water nanofluid. Design/methodology/approach: In this paper, a multiple relaxation times lattice Boltzmann method (MRT-LBM) has been used. Two-component LBM has been conducted to consider the interaction forces between nanoparticles and the base fluid. Findings: Results show that the enhanced Nusselt number (Nu*) increases with the increase in volume fraction of nanoparticles (ϕ) and Ra number and decrease of nanoparticle size (λ). Additionally, the findings indicate that increasing volume fraction beyond a...
Experimental investigation of nanofluid stability on thermal performance and flow regimes in pulsating heat pipe, Article Journal of Thermal Analysis and Calorimetry ; 25 May , 2018 , Pages 1-13 ; 13886150 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Springer Netherlands 2018
Pulsating heat pipe (PHP) is a type of wickless heat pipe that has a simple structure and an outstanding thermal performance. Nanofluid is a type of fluid in which nanoparticles are dispersed in a base fluid and have generally a better thermal conductivity in comparison with its base fluid. In this article, the performance of a nanofluid PHP is investigated. Graphene/water nanofluid with a concentration of 1 mg mL−1 and TiO2 (titania)/water nanofluid with a concentration of 10 mg mL−1 are used as the working fluids. To simultaneously investigate the thermal performance and flow regimes in the PHP, a one-turn copper PHP with a Pyrex glass attached to its adiabatic section is used. A one-turn...
Article Heat Transfer Research ; Volume 49, Issue 16 , 2018 , Pages 1559-1585 ; 10642285 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Begell House Inc 2018
In this work, a solution is applied to investigate the heat transfer characteristics in a pipe with turbulent decaying swirling flow by using the boundary layer integral scheme. The governing equation is solved using the forth-order Runge-Kutta scheme resulting in thermal boundary-layer thickness and dimensionless heat transfer coefficient, namely, the Nusselt number. Both forced- and free-vortex profiles are considered for the tangential velocity component. A comparison of the results obtained for the Nusselt number with available experimental data shows that this scheme has good capability in predicting the heat transfer parameters of swirling flow especially in the entrance region of a...
Numerical investigation of fluid flow and heat transfer characteristics in parallel flow single layer microchannels, Article Scientia Iranica ; Volume 16, Issue 4 B , 2009 , Pages 313-331 ; 10263098 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Heat generation from Very Large-Scale Integrated (VLSI) circuits increases with the development of high-density integrated circuit technology. One of the efficient techniques is liquid cooling by using a microchannel heat sink. Numerical simulations on the microchannel heat sink in the literature are mainly two dimensional. The purpose of the present study is to develop a three-dimensional procedure to investigate flow and conjugate heat transfer in the microchannel heat sink for electronic packaging applications. A finite volume numerical code with a multigrid technique, based on an additive correction multigrid (AC-MG) scheme, which is a high-performance solver, is developed to solve the...