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vapors
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Study of the VAPEX process in fractured physical systems using different solvent mixtures
, Article Oil and Gas Science and Technology ; Volume 63, Issue 2 , 2008 , Pages 219-227 ; 12944475 (ISSN) ; Kharrat, R ; Vossoughi, S ; Ghotbi, C ; Sharif University of Technology
2008
Abstract
In this work, the vapour extraction (VAPEX) process is studied experimentally in a rectangular physical model at moderate-high pressure. The solvent was either pure propane or a mixture of propane/ methane with different compositions. The solvent and carrier gas were totally mixed before injection, so that a solvent with the desired composition flowed through the injector during experiments, and the solvent mixture was in thermodynamic equilibrium before injection into VAPEX cell. Effects of pressure and composition of solvent were studied. Results showed that at a fixed pressure, the process is more effective with pure solvent compared to the use of solvent mixtures. The main feature of...
Analytical solution of chamber effective length in the axial engine
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 12 November 2010 through 18 November 2010, Vancouver, BC ; Volume 7, Issue PARTS A AND B , 2010 , Pages 1095-1102 ; 9780791844441 (ISBN) ; Mozafari, A. A ; Saidi, M. H ; Ghafourian, A ; Sharif University of Technology
2010
Abstract
this research chamber effective length, which is the minimum chamber length required for complete combustion, for a dilute monopropellant spray, constant area, one dimensional and fixed volume engine is analytically predicted. A new evaporation rate in the form of dk +1 relation, instead of d 2 law, is introduced. In case of controlling the vaporization by radiative heat transfer, k is equal to zero, and when molecular processes control the vaporization, k will be equal to unity and in some cases the vaporization data need the value of k greater than one to fit properly to related equation. Development of this approach can be used in design of combustion chambers with optimum length and with...
The effect of oxidation of macroporous silicon on carbon nanotubes growth by TCVD method
, Article Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry ; Volume 37, Issue 6 , 2007 , Pages 489-492 ; 15533174 (ISSN) ; Iraji zad, A ; Taghavi, N. S ; Reyhani, A ; Sharif University of Technology
2007
Abstract
Carbon nanotubes (CNTs) were grown on deposited Ni on macroporous silicon by thermal chemical vapor deposition (TCVD) method using CH4 as the reaction gas. Macroporous silicon was fabricated by electrochemical etching of P-type silicon in organic electrolytes. The effect of oxidation of porous silicon (PS) on growth rate, morphology and structure of CNTs has been studied. The SEM micrographs and Raman spectra indicated that the nanotubes grown on the oxidized PS are more homogeneous and regular than those grown on the pristine PS and growth rate of CNTs grown on oxidized PS higher than those grown on pristine PS. In addition, the CNTs grown on the non-oxidized PS have different morphology...
Vapor absorption into liquid films flowing over a column of cooled horizontal tubes
, Article Scientia Iranica ; Volume 11, Issue 4 , 2004 , Pages 332-338 ; 10263098 (ISSN) ; Babadi, F ; Sharif University of Technology
Sharif University of Technology
2004
Abstract
In this paper, a theoretical analysis of the combined heat and mass transfer over cooled horizontal tubes is presented. The boundary layer assumptions are used for the transport of mass, momentum and energy equations and the finite difference method is employed to solve the governing equations in the absorber tube bundle. The effects of important parameters, such as solution flow rate, absorber pressure and tube radius, are discussed on the overall heat and mass transfer for a tube and tube bundle. © Sharif University of Technology, October 2004
A case study in vapor phase synthesis of Mg-Al alloy nanoparticles by plasma arc evaporation technique
, Article Chemical Engineering Journal ; Volume 259 , 2015 , Pages 918-926 ; 13858947 (ISSN) ; Derakhshan, R ; Mirzaee, O ; Sharif University of Technology
Elsevier
2015
Abstract
Alloy nanoparticles in the Mg-Al system were prepared by plasma arc discharge method from the Mgx to Al (45%
The role of reactants and droplet interfaces on nucleation and growth of ZnO nanorods synthesized by vapor-liquid-solid (VLS) mechanism
, Article Journal of Alloys and Compounds ; Volume 455, Issue 1-2 , 2008 , Pages 353-357 ; 09258388 (ISSN) ; Madaah Hossein, H. R ; Ghamsari, M. S ; Sharif University of Technology
2008
Abstract
Short ZnO nanorods and long ZnO nanowires have been produced on SiO2 and Si substrates by VLS and VS mechanisms via a double tube chemical vapor transport and condensation (CVTC) process. The role of reactants and droplet interfaces on the nucleation and growth of ZnO nanorods have been investigated. A conceptual model for nucleation of ZnO nanorods has been proposed by describing the half-oxidation and reduction reactions at the growth front. The importance of Zn vapor in the nucleation phenomena has been studied by changing starting materials. Atomic force microscopy (AFM), scanning electron microscopy (SEM), and EDX analysis have been used to characterize ZnO nanorods and investigate the...
A multivariable approach for estimation of vapor cloud explosion frequencies for independent congested spaces to be used in occupied building risk assessment
, Article Process Safety and Environmental Protection ; Volume 91, Issue 1-2 , 2013 , Pages 19-30 ; 09575820 (ISSN) ; Nourai, F ; Rashtchian, D ; Sharif University of Technology
2013
Abstract
API Recommended Practice 752 is one of the most referenced practices for evaluating vapor cloud explosion (VCE) impacts to site occupied buildings. This reference introduces generic VCE frequencies for different types of process units that are based on VCE incidents database. Although these reported VCE frequencies are not capable of illustrating all parameters that affect explosion likelihood, they are widely used in risk analysis studies and software packages. This paper delineates the structure of a more realistic method for estimation of local VCE frequencies for independent congested spaces or units as a function of process, site, and meteorological variables. Compared to traditional...
An experimental study on using natural vaporization for cooling of a photovoltaic solar cell
, Article International Communications in Heat and Mass Transfer ; Volume 65 , 2015 , Pages 22-30 ; 07351933 (ISSN) ; Rahimi, M ; Rahimi, A ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
This study attempts to investigate a new way for cooling PV cell using natural vapor as coolant. The performance of solar cell was examined on simulated sunlight. The natural vapor encountered backside of PV cell vertically in various distribution and different mass flow rates. Also, the effect of natural vapor temperature in cooling performance was analyzed. Results indicated that the temperature of PV cell drops significantly with increasing natural vapor mass flow rate. In detail, the PV cell temperature decreased about 7 to 16°C when flow rate reaches 1.6 to 5grmin-1. It causes increasing electrical efficiency about 12.12% to 22.9%. The best performance of PV cell can be achieved at high...
Comparison of synthesis and purification of carbon nanotubes by thermal chemical vapor deposition on the nickel-based catalysts: NiSio2 and 304-type stainless steel
, Article Journal of Applied Sciences ; Volume 10, Issue 9 , 2010 , Pages 716-723 ; 18125654 (ISSN) ; Jafari, A ; Fekri, S ; Shafikhani, A ; Vesaghi, M ; Behzadi, G ; Sharif University of Technology
2010
Abstract
In this study by Thermal Chemical Vapor Deposition (TCVD) method, the synthesis of carbon nanotubes (CNTs) and temperature affects on the grown CNTs on the NiSio2 catalyst and 304-type stainless steel was investigated. The purification of the grown CNTs on the 304-type stainless steel was also investigated in this study. The synthesis and purification of the samples were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), termogravimetric analysis (TGA) and Raman spectroscopy. Our obtained result by SEM and TEM shows that densities of CNTs growth on the 304-type stainless steel are more than the CNTs growth on the NiSio2 catalyst and both of them have...
Application of a new simplified SAFT to VLE study of associating and non-associating fluids
, Article Fluid Phase Equilibria ; Volume 233, Issue 1 , 2005 , Pages 110-121 ; 03783812 (ISSN) ; Taghikhani, V ; Ramazani, A. S. A ; Ghotbi, C ; Sharif University of Technology
2005
Abstract
A new equation of state based on the Statistical Associating Fluid Theory (SAFT) is presented to study the phase behavior of associating and non-associating fluids. In the new equation of state, the hard sphere contribution to compressibility factor of the simplified version of the SAFT (SSAFT) is replaced with that proposed by Ghotbi and Vera. The Ghotbi-Vera SSAFT (GV-SSAFT) was also extended to study the phase behavior of associating and non-associating mixtures. The GV-SSAFT like the SSAFT equation of state has three adjustable segment parameters for non-associating fluids and five parameters for associating fluids. The experimental data of liquid densities and vapor pressures for pure...
Comparative study on adsorption of iodine vapor by silica-supported Cu nanoparticles and micronized copper
, Article Industrial and Engineering Chemistry Research ; Volume 51, Issue 47 , 2012 , Pages 15315-15323 ; 08885885 (ISSN) ; Saket, A ; Ahmadi, S. J ; Hosseinpour, M ; Khanchi, A. R ; Sharif University of Technology
2012
Abstract
The current study is aimed at comparison of adsorption behaviors of silica-supported Cu nanoparticles (Si-N-Cu) and micrometric copper powder (Mi-Cu) for uptake of iodine vapor. The Si-N-Cu was synthesized by the decomposition of aqueous Cu(NO3)2 solution at supercritical condition, followed by reduction of the sample by H 2-N2 mixture. The Si-N-Cu sample with 29.4 nm Cu particles adsorbed 95% of I2 at partial pressure 10-5 bar in 1 h, while the 1 μm Mi-Cu adsorbed 51% of iodine in 6 h, indicating higher yield and faster kinetics of the nanometric sample. Theoretical analysis revealed the existence of a strong thermodynamic size effect in the Cu-I2 reaction system, so that molar |ΔG| for 2...
Growth of tin oxide nanotubes by aerial carbothermal evaporation
, Article Applied Physics A: Materials Science and Processing ; Volume 97, Issue 2 , 2009 , Pages 361-364 ; 09478396 (ISSN) ; Janfeshan, B ; Sadrnezhaad, Kh ; Sharif University of Technology
2009
Abstract
One-dimensional nanostructures of tin oxide nanotubes were fabricated by carbothermal evaporation at 900°C in air. The synthesized film was grown on Au-coated (100) Si substrate. Heterogeneous catalysis by Au/Sn droplets assisted the formation of the tin oxide nanotubes of less than 40 nm diameter at Sn vapor pressures around 1.4×10 -7 Pa. In order to reduce the nanotube diameter further, an increase in the Sn vapor pressure by changing the source materials' ratio seemed viable. © 2009 Springer-Verlag
Sonoluminescence radiation from different concentrations of sulfuric acid
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 80, Issue 4 , 2009 ; 15393755 (ISSN) ; Imani, K ; Silatani, M ; Sharif University of Technology
2009
Abstract
Sonoluminescence (SL) radiation from an argon bubble in water and in different concentrations of sulfuric acid has numerically been studied to quantify the effects of vapor pressure and viscosity of the liquid on cavitation luminescence in a liquid with controllable vapor pressure and viscosity. For the solutions containing the noble gas with low partial pressure (about 4 Torr), it is shown that there exists an optimum acid solution in which both the temperature and the intensity of SL radiation become maximum. The calculations show that the maximum SL radiation is achieved from the solution of around 65% (wt.) H2 SO4, which is in agreement with available experimental results. © 2009 The...
A new two-parameter cubic equation of state for predicting phase behavior of pure compounds and mixtures
, Article Fluid Phase Equilibria ; Volume 242, Issue 1 , 2006 , Pages 19-28 ; 03783812 (ISSN) ; Pazuki, G. R ; Taghikhani, V ; Ghotbi, C ; Sharif University of Technology
2006
Abstract
In this work, a new two-parameter cubic equation of state is presented based on perturbation theory for predicting phase behavior of pure compounds and of hydrocarbons and non-hydrocarbons. The parameters of the new cubic equation of state are obtained as functions of reduced temperature and acentric factor. The average deviations of the predicted vapor pressure, liquid density and vapor volume for 40 pure compounds are 1.116, 5.696 and 3.083%, respectively. Also the enthalpy and entropy of vaporization are calculated by using the new equation of state. The average deviations of the predicted enthalpy and entropy of vaporization are 2.393 and 2.358%, respectively. The capability of the...
Reply to "Comment on 'Role of liquid compressional viscosity in the dynamics of a sonoluminescing bubble'"
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 72, Issue 4 , 2005 ; 15393755 (ISSN) ; Sadighi Bonabi, R ; Sharif University of Technology
2005
Abstract
In reply to the comment of Lu and An on our publication paper [Phys. Rev. E 70, 016304 (2004)], we show that the consideration of water vapor exchange at the bubble interface is essential for obtaining our results and the adiabatic model is too simple to produce the differences. Moreover, in spite of smallness of the compressional viscosity term at the collapse, the illustrated differences are reasonable due to the strong nonlinearity of the bubble dynamics at the collapse and its sensitivity to even small perturbations. We emphasize on the correctness of our calculation results and our simulation programs are now available on the web. © 2005 The American Physical Society
Numerical Modeling of Fuel Droplet Vaporization in Gas Phase at Supercritical Conditions
, M.Sc. Thesis Sharif University of Technology ; Hejranfar, Kazem (Supervisor)
Abstract
The study of evaporation of fuel droplet and determination of the rate of vaporization are important in designing combustion chambers. For achieving high performance of a combustor, the evaporation of fuel droplets takes place within a high pressure environment. At these conditions, the use of low-pressure models is not appropriate and many effects that are assumed negligible at low ambient pressures become very important. For example, the solubility of the ambient gas into the liquid phase is increased by increasing the ambient pressure. In addition, the ideal gas assumption is not valid for these conditions and one should use an appropriate equation of state (EOS) that can predict the...
Synthesis and Characterization of Grapheme Foams Fabricated by Chemical Vaporization Deposition
, M.Sc. Thesis Sharif University of Technology ; Akhavan, Omid (Supervisor) ; Azimirad, Rouhollah (Co-Advisor)
Abstract
The main purpose of this theses is to synthesize graphene by chemical vapor deposition (CVD) of a hydrocarbon gas such as methane on the nickel foam substrate and then to characterize this kind of graphene. Graphene is a single layer of carbon atoms, discovered in 2004, which has led mankind to new eras in all fields by its extraordinary features such as extra high electron mobility, high thermal conductivity, excellent mechanical strength, optical transparence and extra high specific surface. The advantage of this method compared to other methods is that the graphene generated has a better structural quality. Graphene foam firstly, because of the continuity of the foam structure, has better...
Evaluation Of Nano-sorbents for Removal of Ethyl-benzene from Exhaust of Soil Vapor Extraction (SVE)System
, M.Sc. Thesis Sharif University of Technology ; Sayf Kordi, Ali Akbar (Supervisor) ; Alaiee, Ebrahim (Supervisor) ; Tasharrofi, Saiedeh (Co-Advisor)
Abstract
Volatile organic compounds are major cause of air pollution. In this work, Nano porous material named MIL-101(Fe), MIL-53(Fe), MIL-101(Fe) and MIL-88(Fe) as an adsorbent for the removal of ethyl benzene have been synthesized hydrothermally. The materials were characterized by Fourier-transform infrared (FT-IR) spectroscopy, Surface Analysis Systems (ASAP), and x-ray diffraction (XRD) analysis. Adsorption isotherms of ethyl benzene on the materials were measured experimentally in case of 0-1000ppm concentration of ethyl benzene in air and pressure 1 atmosphere. The mixture of air and VOC (ethyl benzene) with concentration of 100, 250, 500 and 1000 ppm and flow rate of 400, 1030, 1525 and 2025...
The study of growth and coagulation of titania nanoparticles by chemical vapor synthesis
, Article Journal of Nuclear Science and Technology ; No.53 , 2010 , pp. 20-29 ; Saberyan, K ; Shahri, F ; Simchi, A. (Abdolreza) ; Sharif Univesity of Technology
Abstract
Chemical Vapor Synthesis route was used for synthesis of titanium dioxide (TiO2) nanoparticles in hot-walled reactor at 800degreeC using TiCl4 as precursor. The effect of processing parameters e.g., temperature and amount of precursor on phase structure, size, purity, coagulation and agglomeration of nanoparticles were investigated in this respect. Also, the H2O effects on the size, crystallinity, phase transformation and purity of nanoparticles were studied. Comprehensive experimental observations were confirmed by transmission electron microscopy, X-ray diffraction analysis and thermal gravimetric-differential thermal analysis results. The obtained results showed that by increasing the...
Comparative study of the grown ZnO nanostructures on quartz and alumina substrates by vapor phase transport method without catalyst: Synthesis and acetone sensing properties
, Article Sensors and Actuators, A: Physical ; Vol. 212 , 2014 , Pages 80-86 ; ISSN: 09244247 ; Mortezaali, A ; Iraji Zad, A ; Sharif University of Technology
Abstract
Uniform layers of ZnO nanostructures were formed on quartz and alumina substrates through a simple vapor phase transport (VPT) method without any catalyst or buffer layer by making proper growth conditions. The effect of substrate on morphology, crystalline structure and photoluminescence spectra has been investigated. Scanning electron microscopy images revealed that morphlogical grwoth depends on used substrate, aligned rods with flower-like bundels and entangled rods are vertically aligned rods on the quartz and alumina substrates, respectively. X-ray diffraction studies showed that grown films on the quartz substrates possess stronger c-axis orientation compared to those on the alumina...