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    Effect of the attraction range of pair potential on the thermodynamic properties of fluids

    , Article Scientia Iranica ; Volume 14, Issue 2 , 2007 , Pages 118-125 ; 10263098 (ISSN) Parsafar, G. A ; Ahadzadeh, I ; Sharif University of Technology
    Sharif University of Technology  2007
    Abstract
    Recently, a new potential model has been proposed for the intermolecular interactions of model pure fluids and it was shown that the derived Equation Of State (EOS), based on this potential, can properly predict the thermodynamic properties of these.fluids. In addition to simplicity and, to some extent, the realistic form, this potential has a parameter (α) which controls the range of the attraction tail. In the first part of this study, the proposed potential and derived EOS are extended to binary mixtures of model fluids. In a similar manner to that of the pure fluids, the results obtained are consistent with the data available from simulation studies. In the second part, after... 

    Investigation of Thermodynamic and Dynamic Properties of Some Solids and Fluids with Nano Dimensions Using Molecular Dynamics Simulation

    , Ph.D. Dissertation Sharif University of Technology Akbarzadeh, Hamed (Author) ; Parsafar, Gholam Abbas (Supervisor)
    Abstract
    The physical characteristics of Pt nanoclusters with different sizes (256-8788 atoms) have been investigated via molecular dynamics simulations. The Pt-Pt radial distribution function, internal energy, heat capacity, enthalpy, entropy of the nanoclusters are calculated at some temperatures. The melting point predicted by the various properties is consistent with each other and shows that the melting temperature increases with the particle size. We have calculated the Gibbs free energy for the Pt bulk and also for its nanoparticle. We have used the thermodynamic integration method to obtain the Gibbs free energy. The total Gibbs free energy is taken as the sum of its central bulk and its... 

    Thermodynamic Properties of Aqueous Electrolyte Solutions Containing Urea

    , M.Sc. Thesis Sharif University of Technology Samieenasab, Ahmad Reza (Author) ; Ghotbi, Siroos (Supervisor) ; Taghikhani, Vahid (Supervisor)
    Abstract
    The behavior of biomolecules in mixtures is affected by the presence of electrolytes. For instance, in the presence of an electrolyte, solubility of most biomolecules like proteins,peptids and amino acids can be increased or decreased. As a biomolecule, urea is a protein denaturant and influences protein folding and protein-DNA binding. The presence of ions can affect the interactions between urea and water In this thesis, experimental data of density and electrical conductance of aqueous solutions of urea-NaCl were obtained at different physical conditions. Density measurement experiments were carried out at different temperatures from 20-40 oC. Apparent and infinite dilution molar volumes... 

    Complexity of Density Dependencies of Thermal- and Internal- Pressure Compared to that of Total Pressure

    , M.Sc. Thesis Sharif University of Technology Sajjadi, Hashem (Author) ; Parsafar, Gholamabbas (Supervisor) ; Goharshadi, Elaheh (Supervisor)
    Abstract
    A simple equation of state (EoS) has recently been introduced (J. Phys. Chem. B 2009, 113, 11977–11987) as (Z-1) v^2=e+f⁄ρ+gρ^2, where Z≡pv⁄RT is the compressibility factor, v=1⁄ρ is molar volume, and e, f, and g are temperature dependent parameters. This EoS has been found to be accurate for all types of nano- and bulk- solids and bulk fluids, in the entire temperature and pressure ranges for which experimental data are reported, except for the isotherms within the critical region.
    The aim of this work is to investigate the validity of a 3-term expression similar to the mentioned EoS for both thermal and internal contributions to the compressibility factor, separately. Such... 

    Calculation of the Thermodynamical Properties of [BMIM][PF6] via Equation of State and Molecular Dynamic Simulations Data

    , M.Sc. Thesis Sharif University of Technology Geraili, Hossein (Author) ; Parsafar, Gholamabbas (Supervisor) ; Tafazzoli, Mohsen (Supervisor) ; Shamkhali, Amir Naser (Co-Advisor)
    Abstract
    In this thesis, We have investigated the accuracy of general equation of state ( EoS III ) and linear isotherm regularity ( EoS I ), introduced on 2009 and 1993, respectively, and the Ghatee’s equation of state ( EoS II ) introduced on 2001, for the pvT data and thermodynamic properties of [BMIM][PF6] ionic liquid. We have carried out simulations at first in a narrow range of pressure, namely within 1-3400 atm and in temperature range from 398 K to 1000 K. The results of fitting of EoS I, EoS II and EoS III into the simulations results, leads to R2 > 0.9936, 0.9800 and 0.9949 respectively, for the pressure range of 1-3400 atm and for the temperature range of 398-1000 K. The results of... 

    Sensitivity analysis of gas turbine fuel consumption with respect to turbine stage efficiency

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 1 , 2012 , Pages 419-423 ; 9780791845172 (ISBN) Zeinalpour, M ; Mazaheri, K ; Irannejad, A ; Sharif University of Technology
    2012
    Abstract
    In this paper, the effect of turbine stage efficiency on fuel consumption of both gas turbines and aerial engines is assessed quantitatively. At the beginning of the gas generator optimization to decrease the fuel consumption, it is necessary to analyze the sensitivity of fuel consumption to its main components efficiencies. This will guide us which component is more important to be optimized. Here a zero-dimensional analysis has been done to determine the effect of turbine stage efficiency on the fuel consumption. Results of this analysis are evaluated in the context of thermodynamic cycle of a gas turbine generator and an aerial engine. As an example, it is shown that if the efficiency of... 

    Modification of a new potential model used for calculation of the second virial coefficient and zero density transport properties

    , Article Molecular Physics ; Volume 104, Issue 20-21 , 2006 , Pages 3269-3280 ; 00268976 (ISSN) Parsafar, G. A ; Shokouhi, M ; Sharif University of Technology
    2006
    Abstract
    A new hard-core potential model was recently used to calculate thermodynamic properties of some model fluids, including equilibrium properties, such as compressibility factor and internal energy. A Lennard-Jones (LJ) like potential has been used to modify the repulsive part of the potential. The modified potential contains five parameters, namely, R, and HS. The parameter is the tail of the attractive branch whose value changes from zero to one. In this work, we have chosen = 1 to make the potential continuous at separation r = R, where the parameter R is the well width. R lies in the range 1.2 to 2.5, and R = 1.3 was found to be the best value for all real gases studied. The parameter is... 

    Estimation of biodiesel physical properties using local composition based models

    , Article Industrial and Engineering Chemistry Research ; Volume 51, Issue 41 , September , 2012 , Pages 13518-13526 ; 08885885 (ISSN) Abedini Najafabadi, H ; Pazuki, G ; Vossoughi, M ; Sharif University of Technology
    2012
    Abstract
    In this study, the local composition based models such as the Wilson, the nonrandom two-liquid (NRTL), and the Wilson-NRF have been applied in correlation and estimation of density, viscosity, and surface tension of biodiesels. The thermodynamic models have been used in correlating the thermophysical properties for 215 experimental data points. These models have the interaction energy between each pair that is considered as adjustable parameters. To decrease the number of these adjustable parameters, it is assumed that the biodiesels are composed of two hypothetical components. The average absolute deviation (AADs) of the correlated density of biodiesels for the Wilson, the NRTL, and the... 

    Computational investigation of graphene behavior under differential water pressure and possible mass transfer influences

    , Article ASME 2016 5th International Conference on Micro/Nanoscale Heat and Mass Transfer, MNHMT 2016, 4 January 2016 through 6 January 2016 ; Volume 2 , 2016 ; 9780791849668 (ISBN) Jafari, S ; Darbandi, M ; Saidi, M.S ; Heat Transfer Division ; Sharif University of Technology
    American Society of Mechanical Engineers  2016
    Abstract
    Because of its unique properties, graphene has attracted the attentions of many academic research groups and recently, the industry. One of the promising applications of the graphene is in micro/nano-sensors, e.g. using it as a pressure sensor. To use it in mechanical-based nano-sensors, it is very important to investigate the mechanical behavior of the nano-sized graphene sheet and its sensitivity to the medium changes applied on its faces. In this work, we use the molecular dynamics MD method and simulate the behavior of graphene sheet under differential water pressure influences. In this regard, a square straight monolayer graphene sheet is placed as a separator diaphragm between two... 

    Simulation of rarefied micro to nano gas flows using improved slip flow models

    , Article 37th AIAA Fluid Dynamics Conference, Miami, FL, 25 June 2007 through 28 June 2007 ; Volume 1 , 2007 , Pages 576-583 ; 1563478978 (ISBN); 9781563478970 (ISBN) Darbandi, M ; Rikhtegar, F ; Schneider, G. E ; Sharif University of Technology
    2007
    Abstract
    If the hydrodynamic diameter of a channel is comparable with the mean free path of the gas molecules moving inside the channel, the fluid can no longer be considered to be in thermodynamic equilibrium and a variety of non-continuum or rarefaction effects can occur. To avoid enormous complexity and extensive numerical cost encountered in modeling of nonlinear Boltzmann equations, the Navier-Stokes equations can be solved considering the concepts of slip flow regime and applying slip velocity boundary conditions at the solid walls. The high-order slip models can, in some cases, extend the range of applicability of the Navier-Stokes equations beyond Kn = 0.1, where the accuracy of first-order... 

    Thermally conductive rubber-based composite friction materials for railroad brakes - Thermal conduction characteristics

    , Article Composites Science and Technology ; Volume 67, Issue 13 , 2007 , Pages 2665-2674 ; 02663538 (ISSN) Shojaei, A ; Fahimian, M ; Derakhshandeh, B ; Sharif University of Technology
    2007
    Abstract
    This study deals with the thermal conductivity of rubber-based composite friction materials used in railroad vehicles. Based on a commercially available railroad friction material, called here base material (BM), various friction materials containing different thermally conductive fillers (Cu, brass, Al, Al2O3 and talc) are fabricated and then their thermal conductivities are measured at various contents of the fillers. Addition of the thermally conductive fillers causes an increase in thermal conductivity of the friction material from 0.48 up to 5.8 W/m K, depending on the type and content of the filler. In addition, the experimental results reveal that the thermal conductivity of the... 

    An investigation into the structure and thermal properties of lead hydroxide

    , Article Scientia Iranica ; Volume 14, Issue 2 , 2007 , Pages 169-173 ; 10263098 (ISSN) Sajadi, S. A. A ; Alamolhoda, A. A ; Hashemian, S. J ; Sharif University of Technology
    Sharif University of Technology  2007
    Abstract
    The compound, lead hydroxide Pb6O4(OH)4, was prepared by a method used for the first time in the authors laboratory. The compound was identified by XRD and it's purity was determined by analytical methods (100%). The thermal characteristics of this compound were investigated by using a thermogravimetry (TGA). This compound was found to be stable at room temperature and at 160°C will decompose completely to produce lead (II) oxide. © Sharif University of Technology, April 2007  

    Effect of model potential of adsorptive bond on the thermodynamic properties of adsorbed CO molecules on Ni(111) surface

    , Article Journal of Physical Chemistry B ; Volume 110, Issue 41 , 2006 , Pages 20435-20444 ; 15206106 (ISSN) Shamkhali, A. N ; Parsafar, G ; Sharif University of Technology
    American Chemical Society  2006
    Abstract
    The effect of anharmonicity on the adsorption of CO molecules on the Ni(111) surface has been investigated. The DFT calculations are used to obtain the effective adsorption potential of the CO molecule on the Ni(111) surface. First, using an appropriate slab model, the geometry of adsorption system corresponding to hep, fcc, bridge, and on-top sites with p(2 × 2) arrangement and coverage of 0.25 ML is optimized by the DFT calculations using a plane wave basis set and ultrasoft pseudopotentials; this gives the hep site as the most stable site with De = 185 kJ/mol, for which the equilibrium distance of CO from the surface and C-O bond length on the surface are found to be 1.31 and 1.192 Å,... 

    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) Dashtizadeh, A ; 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... 

    Influence of additives on the morphology of PVDF membranes based on phase diagram: thermodynamic and experimental study

    , Article Journal of Applied Polymer Science ; Volume 135, Issue 21 , 2018 ; 00218995 (ISSN) Mohsenpour, S ; Khosravanian, A ; Sharif University of Technology
    John Wiley and Sons Inc  2018
    Abstract
    In the present study, the morphology of asymmetric poly(vinylidene fluoride) blend membranes which were prepared by the phase inversion method is rationalized by comparing two non-dimensional number represent thermodynamic and kinetic properties of the prepared membrane. These two parameters change phase diagram and demixing rate between solvent and nonsolvent. TiO2 nanoparticles and polyvinylpyrrolidone were used as additives. Hansen solubility parameters of the components are calculated by Van Krevelen method. Furthermore, kinetic and thermodynamic properties of the prepared solutions are determined by drawing phase diagrams and controlling mass transfer rate during precipitation of... 

    Theoretical Investigation of Carbon Monoxide Adsorption on the Nickel Surface in the Macroscopic and Microscopic Scales

    , Ph.D. Dissertation Sharif University of Technology Shamkhali, Amir Nasser (Author) ; Parsafar, Gholamabbas (Supervisor)
    Abstract
    In this work, CO interaction with macroscopic Ni(111) surface and microscopic Nin (n = 2-4) clusters were investigated. First, the CO interaction with various adsorption sites were studied by DFT methods on Ni(111) surface. On the basis of these calculations, hcp site has the strongest interaction with CO adsorbate. Then, the vibrational frequencies of C=O and adsorptive bond on the hcp site were calculated and the results show that anharmonicity of adsorptive bond is more important than C=O bond. Therefore, three potential models are considered for adsorptive bond and the effect of potential models on its thermodynamic properties was investigated. The results show that the effect of... 

    Property investigation of polypropylene/multiwall carbon nanotube nanocomposites prepared via in situ polymerization

    , Article Polymer International ; Vol. 63, issue. 4 , April , 2014 , pp. 689-694 ; ISSN: 09598103 Jafariesfad, N ; Ramazani, S. A ; Azinfar, B ; Sharif University of Technology
    Abstract
    In this study, polypropylene/carbon nanotube nanocomposites were prepared via in situ polymerization using a bi-supported Ziegler-Natta catalytic system. In this system, magnesium ethoxide and multiwall carbon nanotubes (MWCNTs) are jointly used as catalyst supports. SEM images reveal the distribution and quite good dispersion of MWCNTs throughout the polypropylene (PP) matrix. The thermal properties of the samples were examined using DSC and TGA tests. The results show that the crystallization temperature of the nanocomposites significantly increases while the melting point is not markedly affected. In addition, the thermal stability is improved. The melt rheological properties of PP/MWCNT... 

    Use of atomistic phonon dispersion and boltzmann transport formalism to study the thermal conductivity of narrow Si nanowires

    , Article Journal of Electronic Materials ; Volume 43, Issue 6 , 2014 , Pages 1829-1836 ; ISSN: 03615235 Karamitaheri, H ; Neophytou, N ; Kosina, H ; Sharif University of Technology
    Abstract
    We study the thermal properties of ultra-narrow silicon nanowires (NW) with diameters from 3 nm to 12 nm. We use the modified valence-force-field method for computation of phononic dispersion and the Boltzmann transport equation for calculation of phonon transport. Phonon dispersion in ultra-narrow 1D structures differs from dispersion in the bulk and dispersion in thicker NWs, which leads to different thermal properties. We show that as the diameter of the NW is reduced the density of long-wavelength phonons per cross section area increases, which increases their relative importance in carrying heat compared with the rest of the phonon spectrum. This effect, together with the fact that... 

    SAFT model for upstream asphaltene applications

    , Article Fluid Phase Equilibria ; Volume 359 , December , 2013 , Pages 2-16 ; 03783812 (ISSN) Panuganti, S. R ; Tavakkoli, M ; Vargas, F. M ; Gonzalez, D. L ; Chapman, W. G ; Sharif University of Technology
    2013
    Abstract
    The increasing incidence of flow assurance problems caused by asphaltene deposition during oil production has motivated the development of numerous theoretical models and experimental methods to analyze this complex phenomenon. Even more challenging are the prediction of the occurrence and the magnitude of asphaltene deposition. It is well accepted that precipitation of asphaltene is a necessary condition for deposition. Hence, a significant amount of work has been devoted to the understanding of the conditions at which asphaltene precipitate from the crude oil. Although, several models seem to work well for correlating available data of onsets of asphaltene precipitation, they usually lack... 

    Mixed pressure and AC electroosmotically driven flow with asymmetric wall zeta potential and hydrophobic surfaces

    , Article ASME 2013 Heat Transfer Summer Conf. Collocated with the ASME 2013 7th Int. Conf. on Energy Sustainability and the ASME 2013 11th Int. Conf. on Fuel Cell Science, Engineering and Technology, HT 2013 ; Volume 1 , 2013 ; 9780791855478 (ISBN) Lesani, M ; Sharif University of Technology
    2013
    Abstract
    The present study examines Alternating Current (AC) electroosmotic flows in a parallel plate microchannel subject to constant wall temperature. Numerical method consists of a central finite difference scheme for spatial terms and a forward difference scheme for the temporal term. Asymmetric boundary conditions are assumed for Poison-Boltzmann equation for determining the electric double layer (EDL) potential distribution. The potential distribution is then used to evaluate the velocity distribution. The velocity distribution is obtained by applying slip boundary conditions on the walls which accounts for probable hydrophobicity of surfaces. After determining the velocity distribution...