Sharif Digital Repository

The aim of this research has been to modeling and optimization of steam injected gas turbine with inlet air cooling using absorption chiller. The whole system consists of compressor, combustion chamber, turbine, heat recovery steam generator, absorption chiller and cooling coil. The tasks carried out in this research include four points of view. The thermodynamic, exergetic, thermo-economic and environmental points of view are considered along modeling and optimization process. Design variables including temperature of combustion chamber exhausted gas, pinch point temperature of heat recovery steam generator and steam injection flow rate. Finally this modeling and optimization process is... 

Pipe freezing has become well established in industry as a method of short-termisolation in order to carry out maintenance or repairs. It is often necessary to repair system components without plant shutdown or drainage of system having many piping structures which may have hazardous or expensive fluid. Therefore, a series of tests has been arranged to investigate the ice plug formation in two standard pipes with different diameter size. The freeze zone on the pipe has been created by means of an aluminum jacket which liquid nitrogen flows in it. In the tests the freezing time, amount of liquid nitrogen usage andthe pressure tolerance of ice plug have been determined. Moreover, the numerical... 

Sand production is a phenomenon of producing solid particles together with the reservoir fluid. Material degradation is a key process leading to sanding. Drilling operation, cyclic effects of shut-in and start-up, operational conditions and reservoir pressure depletion may gradually lead to sandstone degradation around perforations and boreholes. Sand production is a major issue and has an adverse impact on production cost that gas and petroleum industry have faced for decades. Corrosion of the pipelines and surface facilities, sand-oil separation cost, repeated shut-in and clean-up of the wellbore are some of the examples. On the other hand, a controlled sanding could be beneficial in... 

Liquefaction is one of the probable consequences of earthquake in soil layers of saturated loose sands. Various aspects of liquefaction have been investigated using different methods of field, laboratory, and numerical studies. Numerical simulation of liquefaction constitutes a major part of these researches. A proper constitutive law must be implemented in the numerical analysis for modeling the complicated behavior of saturated sands during dynamic loading. Simplicity of formulation, limited number of parameters and good performance are the main features of a proper constitutive law. In this study, Endochronic model for simulating liquefaction has been introduced. This model is implemented... 

Lateral spreading is a common mode of earthquake-induced failure that usually occurs as a result of liquefaction in gently sloped sandy layers. Numerical simulation of this phenomenon requires fully coupled analysis of displacement of solid sand particles and pore water pressure under seismic loading. Predicting occurrence of initial liquefaction and sub-sequent ground movement requires employing an efficient and robust constitutive model that can predict the undrained behavior of saturated sand under different conditions. In this study, a fully coupled finite element code “PISA” utilizing a critical state two-surface plasticity constitutive model, proposed by Manzari and Dafalias (1997),... 

Settlement and tilt of structures due to liquefaction of subsoil layers is a major cause of damage during earthquake. Among different soil profile type, two layered soil is very common which was reported many times in differen earthquakes. Settlement of structures was measured by means of empirical methods before which were not viable because they do not consider different effective parameters. Consequently, different experimental studies performed to shed light on different aspects of liquefaction phenomena. In these studies, researchers consider some of the main parameters which have effect on the soil, otherwise, they neglected some important factors. So, numerical procedure is more... 

Nowadays, applications of the synthetic materials are developing in civil engineering projects and widely used in these projects. Therefore, during previous years; use of the Geotextiles as one of the Geosynthetic materials in order to filtration, drainage, separation, soil protection, etc have developed ever-increasing. The goal of this research is modeling and studies of the Geotextiles application in the downstream filter zone of embankment dams in combination with granular materials using FLAC2D software. Gordeh Bin embankment dam situated in West Azerbaijan province has been chosen as case study. In this matter, different models have been made with changes in thickness of the inclined... 

The main purpose of designing machine foundation is to limit its motion to such an amount that not to prevent the perfect workability of machine, not to let the foundation strains exceed the elastic limit and also not to disturb the persons working around the machine. The key note in successfull design of machine foundation, is to precisely analyse the response of foundation to dynamic loads induced by machine operations.The numerical study of shallow foundations response to vertical harmonic loads induced by machinaries have been discussed in this investigation.To aim this purpose, FLACD3D has been utilized in order to 3 dimensionally analyse a continuum medium comprising soil-foundation or... 

Fire is one the events which threatens the very existence of every building, residential, office, industrial or else. However, this threat is more serious with regard to buildings with steel structures. Steel, despite its many advantages over other structural materials, such as having high strength to weight ratio, ductility, toughness and resilience, has the disadvantage of rapidly losing its strength at elevated temperatures, i.e. in fire. Therefore, it is the responsibility of the designer to make the serious decision of whether to use steel, concrete, timber, or other materials for the structure of the building to be designed. Observations made during full-scale fire tests as well as... 

Considering the importance of oil and gas industries in Iran, issues related to drilling and exploitation of oil and gas fields are among the country's priorities and challenges in industries, research centers and universities, and extensive research is conducted in this field. Since during the process of oil production from oil wells and reservoirs, the formation of multiphase flows, including two-phase fluid flow, is inevitable, investigating the behavior of multiphase fluids, which is a branch of fluid mechanics, is of special importance. In this regard, in continuation of the research conducted in the Faculty of Chemical and Petroleum Engineering of Sharif University of Technology, in... 

Nowadays, application of ultrasonic wave technology as a novel method of enhancing oil recovery and also gas an oil well stimulation is prevailing. Not only this method is environment friendly, but also it is economic. Although the application of this method is proved to be of outstanding positive influences in field operations, it suffers from lack of knowledge about the main governing mechanisms and also there are few mathematical models describing the process. In this study it is intended to investigate the role of ultrasonic waves on rate of recovery and the total recovery from porous media. A model is proposed which can predict the recovery at different times of operation. The results... 

Recent studies in nanotechnology field have shown this technology could solve many challenges and needs in oil and gas industry. As yet, many applications of nanoparticles in enhanced oil recovery have been reported. One of the most important applications is wettability alteration due to presence of nanoparticles in injecting fluid, which has recently been studied by several research groups. These studies indicate that, presence of nanoparticles in injecting water would improve oil recovery. However, there is no adequate information about the mechanisms affecting fluid flow in reservoir rock and its mathematical modeling.The aim of this project is to evaluate the effect of injection of... 

Geomechanics has an immense impact on petroleum engineering and applies to the most aspects of petroleum extraction, from exploration and drilling to production and even reservoir abandonment. Studying the mechanical behavior of rocks in hydrocarbon reservoirs and overburden layers will lead to better characterization of mechanical state of the environment. Therefore, a solid understanding of rock mechanical behavior can play a crucial role in reducing operational issues of oil and gas extraction in different phases and prevent extra cost and time consumption. To illustrate, studies of wellbore stability and integrity, casing burst and collapse, drilling optimization, sand production,... 

Air pollution is lateral and inappropriate product of industry and technology development that grows along them, unfortunately. Now its domain extended from local and national issues to global issues. For years like other branches of environmental sciences and other scientific fields, scientists apply formulas and mathematical equations. Nowadays, air pollution modeling is fundamental and powerful tool for air pollution studies, especially in prediction of air pollution conditions, pollutants emission and their concentration under different conditions and arbitrary locations. In this research, numerical modeling of urban air pollutants dispersion is discussed. After validation of results,... 

Access to potable water with standard quality is an inevitable component of human’s lives. Freeze desalination, by consuming lower energy compared to other techniques, relies on the exertion of a cold source which is then accompanied by simultaneous rejection of impurities from water. Regarding this, a numerical study on freeze desalination a hollow cylinder is carried out to determine the effects of the design variables such as heat flux, hydraulic diameter, initial salt concentration, and freezing time on the ice mass, ice salinity, ice generation speed, and Nusselt number on a cold surface of the inner tube. Results show that increasing the value of heat flux from -250 W/m^2 to -1000... 

In this study, single-phase and two-phase, incompressible flow in a non-deformable porous media was modeled and also simulated. The Reynolds numbers have been considered high enough to justify the use of the model including inertial terms. Afterwards, the mass conservative equations were discretized. Then, the numerical model has been developed for heterogeneous porous media. The heterogeneous porous media was comprised by several specified homogeneous regions, each having isotropic transport properties or permeability distribution with applying stochastic methods. The developed numerical model was used for predicting of saturation profile in water flooding process in one, two and... 

Chemical flooding such as surfactant flooding in oil reservoirs can change the wettability and interfacial tension between oil and water and so reduce the residual oil saturation in the reservoir. Some of these materials can be adsorbed a lot on the surface of carbonate rocks, so it is difficult to predict the oil recovery factor in such process. Therefore it is necessary to survey the adsorption amount of surfactants in chemical EOR injections.In this thesis, the adsorption of a nonionic surfactant on the surface of carbonate rock is experimented and the proper model is obtained. Then the surfactant is injected in a core saturated with oil to observe the efficiency of this surfactant in... 

Nowadays, pile usage in construction of deep foundations has increased significantly, instead of shallow foundation in areas that shallow foundations doesn’t provide enough bearing capacity and measuring the velocity and acceleration due to pile driving is very important. Because, all responses of building and individuals located near the pile driving site influenced by these three parameters: pile vertical displacement, peak particle acceleration (PPA) and peak particle velocity (PPV). One can estimates these important parameters by numerical analysis of pile driving process in different distances and depths to determining the effect of pile driving. Compared values obtained from numerical... 

Nowadays, one of the major challenges in the oil and gas industry is sand production, which creates many problems and can complicate the oil and gas production process, so modeling sand production and using models to estimate the start of sand production and also the amount of sand produced can help a lot in the proper management of the reservoir.In this study, first, how to obtain the critical wellbore pressure using the Mohr-coulomb failure criteria and also the Mogi-coulomb failure criteria in different cases, it is explained, that knowing the critical wellbore pressure can be helpful in estimating the start of sand production. Then, how to build a one-dimensional geomechanical model of... 

In this study a locally mass conservative finite volume method (FVM) is employed to simulate the coupled model of flow and geomechanics for the land subsidence problem. At the first step, a FV numerical method is implemented to solve a Biot consolidation model with discontinuous coefficients one dimensionally. The studies show that the FV scheme leads to a locally mass conservative approach which removes pressure oscillations especially along the interface between materials with different properties and yields higher accuracy for the flow and mechanics parameters. Then this numerical discretization is utilized to investigate different sequential strategies with various degrees of coupling...