Search for: gases
0.008 seconds
Total 475 records

    Application of an optimized SLW model to calculation of non-gray radiation heat transfer in a furnace

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 13 November 2015 through 19 November 2015 ; Volume 8B-2015 , 2015 ; 9780791857502 (ISBN) Darbandi, M ; Abrar, B ; Schneider, G. E
    The spectral line based weighted sum of gray gases (SLW) model is considered as an advanced model, which can solve the radiative transfer equation (RTE) in non-gray participating media by dividing the absorption cross section spectrum into a limited number of intervals. Each interval is then treated as a gray gas medium, in which the attributed RTE should be solved separately. Therefore, the SLW model would be computationally more efficient than the other non-gray participating media solvers because it is faced with a small number of RTE solutions. In this work, we present a novel optimized SLW model and applied it to radiation heat transfer calculation in a model furnace. The current... 

    An open source, parallel DSMC code for rarefied gas flows in arbitrary geometries

    , Article Computers and Fluids ; Volume 39, Issue 10 , 2010 , Pages 2078-2089 ; 00457930 (ISSN) Scanlon, T. J ; Roohi, E ; White, C ; Darbandi, M ; Reese, J. M ; Sharif University of Technology
    This paper presents the results of validation of an open source Direct Simulation Monte Carlo (DSMC) code for general application to rarefied gas flows. The new DSMC code, called dsmcFoam, has been written within the framework of the open source C++ CFD toolbox OpenFOAM. The main features of dsmcFoam code include the capability to perform both steady and transient solutions, to model arbitrary 2D/3D geometries, and unlimited parallel processing. Test cases have been selected to cover a wide range of benchmark examples from 1D to 3D. These include relaxation to equilibrium, 2D flow over a flat plate and a cylinder, and 3D supersonic flows over complex geometries. In all cases, dsmcFoam shows... 

    Gas Separation by TEG and Zeolite Na-Y Nano Particles Liquid Membrane

    , M.Sc. Thesis Sharif University of Technology Asadollahi, Mahdieh (Author) ; Bastani, Dariuosh (Supervisor) ; Kazemian, Hossein (Supervisor)
    In this research, in order to investigate the effect of zeolites nanoparticles on the separation performance of a liquid membrane, a TEG/Nano Na-Y was developed. To do this, a high yield nano zeolite Na-Y was synthesized using mid-synthesis addition method . The synthesized samples were characterized by XRD, FT-IR, and SEM (EDX) instrumental techniques. A supported liquid membrane was prepared by impregnating a porous hydrophilic PVDF support with TEG and nano zeolite Na-Y. Permeances of single gas components of CO2, N2 and O2 were carried out at different pressures of 0.8, 1.8 and 3.7 bar. The single gases permeances were found to be: CO2 > N2 > O2. The results were shown that higher weight... 

    Synthesis & Characterization of Nano Zeolite SAPO-34 Membranes on Alumina Supports and Evaluation of Their Performance for Gas and Vapor Separation

    , M.Sc. Thesis Sharif University of Technology Dargahi, Mahdi (Author) ; Soltanieh, Mohammad (Supervisor) ; Kazemian, Hossein (Supervisor)
    A Novel synthesis method to assemble of nano crystalline SAPO-34 molecular sieves crystalline is successfully developed at a supercritical condition. The environmental and operating conditions are investigated through a Taguchi L-9 orthogonal array and optimum synthesis conditions in order to reach highest crystallinity and smallest crystalline. The products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), thermal method of analysis (e.g. TG-DTA), and infra red spectroscopy (FT-IR) techniques. In comparison to conventional hydrothermal methods, using a supercritical hydrothermal approach leads to the higher purity, reduced particle size, and change of... 

    Assessment of Greenhouse Gas Mitigation Potential from Energy System

    , M.Sc. Thesis Sharif University of Technology Talaei, Alireza (Author) ; Soltanieh, Mohammad (Supervisor) ; Saboohi, Yadollah (Supervisor)
    Globally energy system is the main source of green house gas emission. 60-90 percent of manmade CO2 is due to energy sector. Pollutants like NOx, CO, Non Methane Hydrocarbons which may cause indirect effect on climate system are mainly emitting from energy sector. Gas, Oil and Coal extraction and transmission are responsible for more than 15% of Methane emission globally. Therefore it is important to consider all types of GHGs emission as well as all sectors of energy system to assess the GHGs mitigation potential throughout the energy system. Considering the significance of energy sector in GHGs emission, in this study we developed an optimized model for Iran’s energy sector in which we ran... 

    The dependency of relative permeability on dominated flow regimes under gas gravity assisted flow

    , Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Volume 33, Issue 2 , Oct , 2011 , Pages 101-113 ; 15567036 (ISSN) Rostami, B ; Kharrat, R ; Pooladi Darvish, M ; Ghotbi, C ; Sharif University of Technology
    Gas-oil relative permeability is essential for performance predictions of reservoirs with solutions for gas drive, gas cap expansion, or gas injection. The nature of flow in reservoir is determined by the interplay of relative permeability and viscous, gravity, and capillary forces. Displacement experiments of the gas-oil system are performed on long core scale models by varying the petrophysical properties and flow conditions. Experiments are conducted in situations where capillary, gravity, and viscous forces are comparable. The effect of destabilized front velocity on relative permeability and residual saturation is investigated. The results indicate that the relative permeability varies... 

    A new approach to model sensitivity of graphene-based gas sensors

    , Article Semiconductor Science and Technology ; Volume 30, Issue 4 , March , 2015 ; 02681242 (ISSN) Ghadiry, M ; Ismail, R ; Naraghi, B ; Taheri Abed, S ; Kavosi, D ; Fotovatikhah, F ; Sharif University of Technology
    Institute of Physics Publishing  2015
    Carbon-based sensors are attractive because of their excellent sensing capability. In this paper, we propose a new approach to analytically model the sensitivity of these devices based on graphene. The model relies on the surface potential and current of the device. For the first time, we included ionization in the modelling and examined the importance of this effect. In order to validate the model, the results are compared with experimental data from a fabricated device  

    Assessment of Global Potential of Biohydrogen Production from Agricultural Residues and Its Application in Nitrogen Fertilizer Production

    , Article Bioenergy Research ; 2019 ; 19391234 (ISSN) Karimi Alavijeh, M ; Yaghmaei, S ; Mardanpour, M. M ; Sharif University of Technology
    Springer  2019
    In the present study, an attempt was made to investigate the potential of some of the major world’s crops, including wheat, corn, rice, barley, sugarcane, sugar beet, potatoes, and oats, to produce biohydrogen. The collectable amount of agricultural residues that could especially be used to produce hydrogen was estimated in Africa, Asia, Central America, Europe, Northern America, Oceania, and South America, and the potential amount of ammonia as the main nitrogen fertilizer was estimated. Double exponential smoothing method was employed to forecast the future crop production and area harvested. It was calculated that about 10.56 (in 2013) and 15.5 (in 2030) Mt of biohydrogen and 59.84 (in... 

    Modelling and simulation of syngas unit in large scale direct reduction plant

    , Article Ironmaking and Steelmaking ; Volume 30, Issue 1 , 2003 , Pages 18-24 ; 03019233 (ISSN) Farhadi, F ; Motamed Hashemi, M. Y ; Bahrami Babaheidari, M ; Sharif University of Technology
    IOM Communications Ltd  2003
    The production of reducing gas is usually a bottleneck to capacity increase in direct reduction plants. Modelling and simulation of reducing gas production result in better design and operation of these plants. In the present work, a mathematical model is discussed that relates to a Midrex reformer, which is different from conventional steam reformers in some respects. Both process side and furnace side have been included in an integrated model. Simulation results have been tested against available data from an actual plant. The model predictions have been found to be reasonably accurate. The effects of three process variables, feed gas temperature, feed gas pressure and excess air, on... 

    Developing A Model for Evaluation of Energy Recovery From Flared Gas

    , M.Sc. Thesis Sharif University of Technology Vahabpour, Amir (Author) ; Saboohi, Yadollah (Supervisor) ; Sattari, Sourena (Co-Advisor)
    According to the World Bank, nearly 154 billion cubic meters of gas is flared in the world every year. Iran is known as the third gas flaring country by burning about 11.4 bcm (approximately 8% of the total amount). Flared gas is a rich gas and has a high heating value. Therefore flaring it equals to waste of a valuable source of energy. In addition, serious concerns about its environmental effects due to emission of considerable amounts of CO2, SOx, NOx and other pollutants, makes it necessary to find a solution to reduce gas flaring. There are several ways for flared gas utilization including electricity generation, injecting into oil wells for enhanced oil recovery, gas processing and... 

    Developing a New Method to Estimate Taxing Electricity Sector Carbon Emissions based on Social Cost of Carbon Emissions

    , M.Sc. Thesis Sharif University of Technology Shahbazi Seifabad, Ashkan (Author) ; Avami, Akram (Supervisor) ; Moeini Aghtaei, Moein (Co-Supervisor)
    Controlling, managing, and mitigating the emission of greenhouse gases, especially carbon dioxide, which are produced by human activities, are one of the main concerns of researchers today. Market-based methods are one the successful methods to enhance controlling, managing, and mitigating carbon dioxide emissions, among which the carbon tax has received more attention. Increasing clean technologies in the electricity network to the reduce the emissions of the electricity industry may reduce the carbon tax rate. In this regard, the life cycle analysis makes it possible to consider the emissions of the life cycle. The present model is applied for two representative days of Iran's electricity... 

    DSMC simulation of heat transfer in subsonic rarefied gas flows through micro/nanochannels imposing a constant inflow/wall temperature difference

    , Article 41st AIAA Fluid Dynamics Conference and Exhibit ; 2011 ; 9781600869471 (ISBN) Darbandi, M ; Karchani, A ; Akhlaghi, H ; Mosayebi, G ; Schneider, G. E ; Sharif University of Technology
    We use the direct simulation Monte Carlo (DSMC) method and investigate the subsonic rarefied gas flow through micro/nanochannels, imposing a constant pressure ratio and a constant temperature difference between the inflow and wall temperature. We further study the heat transfer characteristics of subsonic nitrogen gas flow under this imposed temperature difference. We show that, specifying a higher temperature magnitude would lead to more rarefactions even imposing a fixed temperature difference. This consequently results in a higher wall heat flux rate for a fixed inflow-wall temperature difference. Our investigating shows that the number of simulated particles need to increase suitably if... 

    A three-stage scenario based operational performance test approaches for production capacity enhancement: Case study on the 5th refinery of South Pars Gas Complex in Iran

    , Article Journal of Natural Gas Science and Engineering ; Volume 27,Part 3 , November , 2015 , Pages 1758-1770 ; 18755100 (ISSN) Fahimirad, M ; Farzad, S ; Moghaddam, S. N ; Saremi, H. S ; Sharif University of Technology
    Elsevier  2015
    In this work, the possibility of capacity enhancement in the South Pars Gas Complex of Iran has been studied. Mass balance is studied and data validation and reconciliation have been carried out in 5th refinery of South Pars Gas Complex in order to achieve the reliable data of the plant. Then the possibility of capacity increase has been studied, taking into account the important parameters such as alteration of the plant pressure profile. Calculation of the key parameters for different equipment at higher feed rate, specified the unit of operations which may have trouble during the capacity enhancement. The performance of export gas compressors, dehydration unit and High-Integrity Pressure... 

    Joint estimation of absolute and relative permeabilities using ensemble-based Kalman filter

    , Article Journal of Natural Gas Science and Engineering ; Volume 26 , September , 2015 , Pages 1232-1245 ; 18755100 (ISSN) Jahanbakhshi, S ; Pishvaie, M. R ; Boozarjomehry, R. B ; Sharif University of Technology
    Elsevier  2015
    An ensemble-based, sequential assimilation procedure is developed and successfully applied to estimate absolute and relative permeabilities jointly under multi-phase (oil, gas and water) flow condition in the porous media. Two-phase oil-water and gas-oil relative permeabilities are represented by power-law models, and Stone's Model II is used to calculate three-phase oil relative permeability. Prior absolute permeability field is also generated with isotropic Gaussian covariance. The proposed method is validated by a twin numerical setup with three different case studies, in which a synthetic 2D reservoir under multi-phase flow condition is considered. In the first case, there is... 

    Mathematical modeling of a slurry bubble column reactor for hydrodesulfurization of diesel fuel: Single- and two-bubble configurations

    , Article Chemical Engineering Research and Design ; Volume 100 , August , 2015 , Pages 362-376 ; 02638762 (ISSN) Khadem Hamedani, B ; Yaghmaei, S ; Fattahi, M ; Mashayekhan, S ; Hosseini Ardali, S. M ; Sharif University of Technology
    Institution of Chemical Engineers  2015
    In this investigation, a mathematical model for HDS of diesel fuel in a slurry bubble column reactor was developed. The model is based on the axial dispersion of the heterogeneous gas flow regime, which includes two various bubble classes: large (20±70mm) and small (1±10mm). By assuming only large or large plus small bubbles in the column, single- and two-bubble class mode equations are developed. The developed models to solving the mass and enthalpy balances from which the sulfur conversion was obtained that undertaken. The chemical kinetics over NiMoS/γ-Al2O3 catalyst were undertaken for the reaction rate of the involved reactions. The reactor operating conditions... 

    Prediction of water content of sour and acid gases

    , Article Fluid Phase Equilibria ; Volume 299, Issue 2 , December , 2010 , Pages 171-179 ; 03783812 (ISSN) Zirrahi, M ; Azin, R ; Hassanzadeh, H ; Moshfeghian, M ; Sharif University of Technology
    Estimating the feasibility of acid gas geological disposal requires the knowledge of the water content of the gas phase at moderate pressures and temperatures (typically below 50MPa, below 380K) and up to 6mol NaCl. In this paper, a non-iterative model is developed to predict the water content of sour and acid gases at equilibrium with pure water and brine. This model is based on equating the chemical potential of water and using the modified Redlich-Kwong equation of state to calculate the fugacity of the gas phase. The water content of pure CH4, CO2 and H2S are represented with average absolute deviations of less than 3.36, 7.04 and 8.4%, respectively. Experimental data of the water... 

    Study and full simulation of ten different gases on sealed Multi-Wire Proportional Counter (MWPC) by using Garfield and Maxwell codes

    , Article Applied Radiation and Isotopes ; Volume 115 , 2016 , Pages 289-294 ; 09698043 (ISSN) Ebrahimi Shohani, M ; Golgoun, S. M ; Aminipour, M ; Shabani, A ; Mazoochi, A. R ; Maghsoudi Akbari, A ; Mohammadzadeh, M ; Davarpanah, M. R ; Sardari, D ; Sadeghi, M ; Babapour Mofrad, F ; Jafari, A ; Sharif University of Technology
    Elsevier Ltd 
    In this research gas sealed Multi-Wire Proportional Counter (MWPC) including blades between anode wires and beta particles of 90Sr with 196 keV mean energy were considered. Ten different gases such as Noble gases mixtures with methane and several other pure gases were studied. In this type of detector, by using Garfield and Maxwell codes and for each of the gases, variation of different parameters such as first Townsend, electron attachment coefficients with variable electric field and their effects on pulse height or collected charge and in turn on Signal to Noise Ratio (SNR) were studied. Also the effect of anode voltage and its diameter and the pressure of gas on the pulse height were... 

    Shock-wave-detection technique for high-speed rarefied-gas flows

    , Article AIAA Journal ; Volume 55, Issue 11 , 2017 , Pages 3747-3756 ; 00011452 (ISSN) Akhlaghi, H ; Daliri, A ; Soltani, M. R ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2017
    This paper introduces a shock-wave-detection technique based on the schlieren imaging for continuum and rarefied-gas flows. The scheme is applicable for any existing two-dimensional flowfields obtained by experimental or numerical approaches. A Gaussian distribution for a schlieren function within the shock-wave region is considered. This enables the authors to access any desired locations through the shock (e.g., shock center, or leading- and trailing-edge locations). The bow shock-wave profile is described via a rational function, which could be employed for the estimation of shock angle. The relation between pre- and postshock flow properties along the shock wave with a high resolution... 

    Pore-scale modeling of rarefied gas flow in fractal micro-porous media, using lattice Boltzmann method (LBM)

    , Article Journal of Thermal Analysis and Calorimetry ; Volume 135, Issue 3 , 2019 , Pages 1931-1942 ; 13886150 (ISSN) Rostamzadeh, H ; Salimi, M. R ; Taeibi Rahni, M ; Sharif University of Technology
    Springer Netherlands  2019
    Due to the widespread use of rarefied gas flow in micro-porous media in industrial and engineering problems, a pore-scale modeling of rarefied gas flow through two micro-porous media with fractal geometries is presented, using lattice Boltzmann method. For this purpose, square- and circular-based Sierpinski carpets with fractal geometries are selected due to their inherent behavior for real porous media. Diffusive reflection slip model is used and developed for these porous media through this study. With this respect, the planar Poiseuille flow is selected as a benchmark and validated with the literature. The effect of Knudsen number (Kn) on the permeability is investigated and compared in... 

    Polymeric like carbon films prepared from liquid gas and the effect of nitrogen

    , Article Applied Surface Science ; Volume 254, Issue 20 , 15 August , 2008 , Pages 6441-6445 ; 01694332 (ISSN) Ghodselahi, T ; Vesaghi, M. A ; Sharif University of Technology
    Elsevier  2008
    Polymeric like carbon (PLC) films are grown by a capacitance coupled RF-PECVD on the grounded electrode at room temperature from liquid gas (40% propane and 60% butane) in two regimes with nitrogen and without nitrogen gas. Films are characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Fourier transform infrared (FTIR) absorption and Raman spectroscopy. The result of FTIR analyses indicates that more than 90% of hydrogen atoms are bonded to carbon with sp 3 hybridization. The abundance of CH 3 is more than that of CH 2 and this one is more than that of CH for carbon with sp 3 hybridization in these films. The C 1s line of the XPS spectra is deconvoluted to...