Sharif Digital Repository

In this work, by considering the medium effects and adding the long−range interactions to the isolated pair potential, the concept of the extended effective pair potential of the Lennard−Jones (12, 6, 3) has been purposed for dense systems. Due to lack of any information regarding the parameters of this potential for any fluid, the purpose of this work is to introduce a new method to calculate these parameters using experimental pVT data. Since the extended potential of Lennard− Jones (12, 6, 3) is a general function based on which that an equation of state can be derived (equation of state III) predicts many properties of dense systems that no deviation is observed. Also it doesn’t have... 

In this thesis, we use two simple simulation models for ionic liquids, and the efficiency of the Lennard Jones equations and the state equation obtained from this potential were investigated. Then, using these models, the temperature-dependent coefficients were calculated in two equations at different temperatures, and then analytical expressions were reported to them. Given that ion fluid data is reported only in a small range of densities, these data were used to evaluate the equations used, using a model in a wider range of densities. For this purpose, simulation of molecular dynamics simulation data was simulated. In these two models, the relative size of cations and anions is different.... 

Due to their low volatility, negligible flammability, and high regeneration capacity, ionic liquids have attracted a lot of attention in chemical and process engineering fields. Regarding the limited access to the laboratory facilities, developing theoretical methods such as equations of state is important in this research field. Thus, data for density and viscosity of pure ionic liquids and vapor pressure data for binary mixtures of ionic liquids and acidic gas have been collected and validated from the IL Thermo website for 42 ionic liquids. By consideration of theoretical studies and comparison of the performance of different cubic equations of state in predicting the aforementioned... 

The cubic equation of state (CEOS) is a powerful method for calculation of (vapor + liquid) equilibrium (VLE) in polymer solutions. However, the traditional mixing rules are not appropriate to extend the CEOS to non-ideal mixtures such as polymer solutions. For better prediction of (vapor + liquid) equilibria in polymer solutions, it is better to use mixing rules based on Excess Gibbs free energy function, GE. Choosing an appropriate excess Gibbs free energy for a mixing rule is a major step. In this work, by using three EOS (PRSV, Dashtizadeh and SRK) with FH-NRTL-NRF excess Gibbs free energy model and Wong–Sandler mixing rule, the EOS/GE method is applied for prediction of phase... 

A Specific process centrifugal compressor is upgraded. The operating range and efficiency pattern are increased. A one-dimensional performance prognosis tool (CCPP) is developed. The tool uses mean streamline method as the analysis model. Since the working media has various components, a complete equation of state is utilized to model the thermodynamic behavior of the real gas in super critical pressures. The performance of the base-line compressor is deyermined. The performance prognosis tool is validated with available experimental data. Upgrade road map and methodology were introduced in accordance to domestic requirements. The performance of the upgraded compressor is investigated and... 

A general regularity has been found based on an effective pair potential of Lennard-Jones LJ (12, 6) for both dense nonmetallic and nonionic fluids and solids; namely, (Z-1)V2 linearly varies with respect to ρ2, this equation of state (EoS I) is known as LIR. The other equation of state (EoS II), according to wich the isotherm of (Z-1)V2 is linear in term of 1/ρ, wich gives a good description for the metallic and ionic fluids and solids. This equation of state was suggested based on an effective pair potential of LJ (6, 3). Unexpectedly, solid and liquid Ne indicates a significant deviations from EoS I. Recently, a general equation of state (EoS III) based on an effective near-neighbor pair... 

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... 

In 2009, a general equation of state (EOS-III) based on an effective near-neighbor pair interaction of an extended Lennard-Jones (3, 6, 12) type has been introduced as : , where is the compressibility factor, p and ρ stand for pressure and molar density , respectively, T is Temperature , and e, f and g are the temperature dependent coefficient of the equation of state . the Z_th and Z_in are the thermal and internal contributions of pressure in the compressibility factor, respectively. this equation of state gives a good description of all types of nano- and bulk –solid and bulk fluid at entire temperature and pressure ranges for which thee is experimental data. Investigation show that... 

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... 

In this research, a method based on the modified Enskog theory (MET) and some equations of state has been used to calculate the transport properties of some dense fluids. The main limitation to using the MET is the lack of experimental data for the co-volume, b0, that are substituted from the hard sphere (HS) theory, and the zero density transport properties that are substituted from the kinetic theory of gases for the HS in the MET expression, because of the fact that dense fluids behave more and less like a HS fluid. So a quadratic expression for both ηY/(√T ρ) and λY/(ρ√T) (C_(V,m)+ (9/4)R) in terms of Y at high densities (ρ > ρc) for each isotherm is expected, where Y = (T (∂p/∂T))/ρRT... 

In this thesis heat transfer coefficient and temperature distribution of two Non-Newtonian and a Newtonian fluids in stirred vessel are investigated using Computational Fluid Dynamic (CFD). This vessel is agitated with new impeller called MAXBLEND. Non-Newtonian fluids are aqueous solutions of carboxymethyl cellulose 1.5%w/w and xanthan gum 3% w/w and Newtonian fluid is glycerin. This vessel is simulated in laminar regime with Reynolds number less than 14. The results of simulation are compared with correlation proposed by Kawase et al.
Furthermore as a new research for this impeller, the effects of vessel diameter and position of impeller in the vessel on heat transfer coefficient are... 

Helium gas is the working fluid in common Pulse Tube Refrigerators (PTRs) due to its brilliant properties in reaching cryogenics temperature as low as 4 K. Generally ideal gas equation of state has been used to evaluate thermodynamic performance of He. However using ideal gas equation of state for He in 10 bar and 5 K causes considerable error on estimation of density. The objective is to use real gas equation of state for temperatures near zero Kelvin. This approach makes an accurate prediction of PT cooling capacity and COP. In this thesis the objective is to realize the most relevant equations of state describing the proper behavior of He in the regions of operating point of PTR. Later on... 

Economic loss due to wax precipitation in oil exploitation and transportation has reached several billion dollars a year recently. Development of amodel for better understanding of the process of wax precipitation is therefore veryimportant to reduce the loss.Currently, there are two types of soild models. One is the solid-solution model, and the other is the multisolid-phase model.In this work, a new thermodynamic model that combines the two methods mentioned above, has been presented. The PC-SAFT EOS is used to describe the vapor, liquid and wax phase.SAFT equations describe the phase behavior of large molecules accurately. Intermolecular forces in wax phase are caused by London and Van-... 

experimental data of crude oil for viscosity are available in limited conditions of temperature and pressure. Therefore, the use of empirical equations and relations to predict it at temperatures and pressures beyond the temperature and pressure of the reservoir is inevitable. In order to reduce the cost of the laboratory, the use of a comprehensive model in this project is considered. For this purpose, using two theories of friction and free volume, the Peng Robinson and PC-SAFT equation of states and genetic algorithms and particle swarm optimization are widely used to calculate the viscosity of pure hydrocarbons, binary mixtures of hydrocarbons and crude oil have been used. Obviously, by... 

Inrecent years,research onionic liquidsarehighly developed. Because ofthe uniqueproperties ofionic liquidssuch asnegligiblevapor pressureandthermalstability for use inlarge areasofmajor industries have been considered.However,ionic liquids because they have lessenvironmental wasteas an alternative to convention alorganic solventssuch asaminesalkanolanarise.Ionic liquid sassolventsfor theremoval ofacid gases such as water and gasare investigated. The solubility of CO2 and H2S in the [Emim] [OTF] (1-ethyl-3-methylimidazolium triflate) in the temperature range 303.15 to 343.15 K and pressures up to 2 MPa has been studied experimentally. In order to capture modeling, the model equations of state... 

The usual method for determination of pure component parameters of SAFT-type Equation of State (EoS) is to fit them to experimental vapor pressure and liquid density data. Since high-molecular-weight compounds, like polymers, do not have a detectable vapor pressure, there is a need for a predictive calculation method for parameters of polymers and other complex compounds. In 2008, Tihic et al. proposed a Group Contribution (GC) method for estimating molecular parameters of PC-SAFT EoS. In this thesis, it is attempted to extend the suggested method of Tihic et al. by adjusting molecular parameters of PC-SAFT EoS for about 120 new non-associating compounds using experimental data extracted... 

Flow analysis in and out of the pressure-swirl injector in supercritical condition is investigated in this thesis. These injectors widely are used in different industries such gas turbine combustion chamber and liquid fuel rockets. Flow simulation in these injectors is so complex because of existence of gas core in axial region and high swirl and axial speeds in injectors. Unlike subcritical condition, droplet and ligament don’t form in supercritical condition so injector performance represents with two parameters including liquid film thickness in vortex chamber and liquid spreading angle. Mass flow, geometric constant, length and the distance between tangential inlet and injector head, are... 

Prediction and prevention from asphaltene deposition is an essential topic in oil production systems that can enormously increase oil production costs. Many studies have been done to understand and predict the behavior of asphaltene-containing oils. Prediction and investigation of asphaltene precipitation are required to predict the asphaltene deposition problem. Changes in temperature, pressure, and composition can cause precipitation, and these changes are inevitable during production. This dissertation compares the thermodynamic models that can simulate asphaltene precipitation. Firstly, A comprehensive review was done to extract the maximum amount of experimental data from the literature... 

In recent decades, there have been great efforts to simulate flow in hydrocarbon reservoirs and oil recovery processes. Compositional model is one of the most advanced models for this purpose. In this model nonlinear mass conservation equations for multicomponent flow have to be solved along with thermodynamic equilibrium constraints. In most compositional simulators, an equation of state is used to determine phase behavior of hydrocarbon mixtures. In this work an efficient two-phase compositional model for both immiscible and miscible fluid flows in porous media is presented. The solution algorithm employs the so-called Implicit Pressure Explicit Saturation (IMPES) method. To determine the...