Sharif Digital Repository

Nowadays, there is a focus on developing a propulsion system with higher efficiency and performance in comparison to conventional systems. Many diverse systems have been designed for the vessel propulsion and everyday, utilizing new ideas, their performance and energy consumption are being improved. Direct use of steam energy is a noble and new idea. In this research, the steam jet propulsion system has been explained and current worldwide research on the topic has been investigated. Considering the shortage of primary data in the field and the novelty of subject, required information for the manufacturing of a sample model of this special propulsion system has been gathered and a design for... 

In the absence of appropriate control, several accidents in the nuclear power, lead to serious consequences including core melted and radiation leakage outside reactor containment. In all these events, when core melted, the reactor operation is always finished and all efforts are then directed to environmental impacts of radioactive materials to the external environment. However, the occurrence of events that would bypass reactor containment, have special significance, because all possible efforts in order to limit the leakage of radioactive materials to the external environment are ineffective. In this respect the occurrence of such incidents, as most of which is considered the worst... 

Steam-Assisted Gravity Drainage (SAGD) is one of the best and the most effective methods of enhanced oil recovery (EOR) which is used in the production from Heavy Oil Reservoirs which constitute large amount of oil throughout the globe. In a typical process of SAGD, steam is injected into a horizontal well and the oil is produced several meters deeper in the ground. In order to increase the Recovery of this process, it is better to review on the Pre-heating methods around the injecting and producing wells. Pre-heating is important when the viscosity of the oil is large enough to prevent oil from any motion at the beginning of the SADG operation, and makes it necessary to to use a Pre-heating... 

Due to nuclear power plants’ growing roll in providing energy, analyzing probable accidents and their prevention is of vital importance. The thermal-hydraulic shock accident which happened in Bushehr nuclear power plant deaerator has been simulated in this study. Steam bubble collapsing which takes place in two phase medium by mixing steam and subcooled water leads to this kind of shock causing financial and physical irreparable damage in nuclear power plants. For carrying out this simulation, first an steady state model of the deaerator was run using RELAP5 code and then using this model and other plant’s data such as the ropert of the accident and plant’s Final Safety Analysis Report... 

The present research deals with the effect of steam injection to gas turbine engines. First, a comparison is made across the possible positions in the gas turbine for steam injection. Commercial software is used to investigate the pros and cons. Second, the investigation is focused on an industrial 4 MW gas turbine engine. Classical cycle and sensitivity analysis are performed and the operating envelope of the gas turbine engine with steam injection at various operating states as well as different environmental conditions is determined. Finally, a simulator based on Matlab Simulink is developed to examine the impact of different design and thermodynamic conditions of steam injection to the... 

In this research, room-temperature flexible humidity sensors using graphene oxide (GO) and partially reduced grapheme oxide (PRGO) are reported. Sensing layer was deposited onto Kapton substrate by spin coating method. Topography of the sensing layer was observed by Optical Microscopy, Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Partial reduction of the GO was confirmed by X-ray Diffraction (XRD) data. Humidity sensing properties of the samples that were annealed in different temperatures in the range of 125-200 were measured at room temperature. The sample which was reduced at 125 presented higher response about 106% and shorter recovery time of about 65 s.... 

During the operation of a nuclear power plant, the reactor pressure vessel (RPV) is exposed to a variety of pressure and thermal stresses and neutron radiations. This will cause the loss of the initial strength of the reactor vessel component. During the occurrence of some of accidents, an excessive cooling of the coolant inside the RPV takes place which in the term is called overcooling transients. In addition, in some of these events, a break in a section of the circuit will reduce the water level at the core of the reactor. By reducing the water level, the existing emergency makeup water systems are activated and inject water into the reactor. The temperature of the added water is much... 

Air-cooled condenser is widely used in thermal power plants as its main cooling system. However, the thermal capacity of air-cooled condensers reduces considerably in environmental wind drafts. So, the purpose of this study is to find practicable solutions to minimize the mal-performance of air-cooled condensers in windy conditions in either design or off-design conditions and consequently prevent the related steam turbines power reduction. The target combined cycle power plant consists of 4*160 MW steam turbines and 4 air-cooled condensers in its steam cycle part. This research presents two general and practical remedies, which are also applicable to many different powerplants irrespective... 

One of the most important production mechanisms of fractured reservoirs is wettability alteration. Since most fractured reservoirs are carbonate, and thus are often oil-wet; production of these reservoirs is facing their special challenges. Since most of our country reservoirs are fractured carbonate type, determination of the exact mechanisms of their production is necessary. Thermal EOR methods traditionally have been welcomed by big oil companies. Also, these methods of enhanced oil recovery techniques, have a much greater share in the production history of all EOR methods, rather than other EOR methods. Exponentially decreasing of oil viscosity on heating, is the main reason for using... 

Designing a part of an on site repair system for refurbishing steam turbine high pressure control valve has been done in this project. The main role of this control valve is to control the input flow to the turbine in different working condition . However, due to high temperature and pressure, the seat is exposed to erosion. R epairing this part in workshop requires great amount of time and cost, because the valve is a part of the turbine body and must be cut and rewelded to the turbine body. S o using an on-site repair method is highly needed. In addition, due to the limited visibility and access to the valve seat, and accurate... 

Hybrid Solid Oxide Fuel Cell-Micro Gas Turbine systems(SOFC-MGT) present opportunities for improvement over conventional systems, including high efficiency, cogeneration, and the potential for low carbon emmisions. In order to advance toward commercialization, Hybrid systems need to model under design point and off-design situations that maintain safe and efficient operations, also exhibiting favorable exergetic and economic performance. The present work investigates the hybrid SOFC-MGT performance and effects of steam injection, humidity effect, and fuel change in the system. The 1-D model of SOFC stack has been developed in EES Code and then coupled with a microturbine’s components with... 

Power generation stations, which are commonly called power plants, are treated as the core module of power systems and are in charge of producing power to be transmitted and distributed to the end consumers. As the beating heart of power industry, power plants need to be available and reliable all the time and so do their constituent components since the need for reliable electricity, nowadays, is ever increasingly highlighted. The reason lies in the rapid jump of population growth in one hand and the incredible amount of damages as a consequence to the power interruptions due to the power plant component outages, if happened, on the other one. So, power plants have to be kept within a... 

Combined cycle power plants consist of three main sections, namely gas turbine, Heat Recovery Steam Generator (HRSG) and steam turbine. Occurring failure in HRSG causes the steam turbine trip, so the reliability assessment of HRSG has a great importance for forecasting the probability of occurring failure and also reducing failure causes. In this project, the reliability of HRSG considering effects of aging phenomenon, maintenance and, environmental and operational conditions on reliability is modeled. Afterward a method to estimate the model parameters is introduced. Using present method, failure data of six HRSGs of a plant each with a capacity of 50 MW is analyzed and the model parameters... 

Nowadays, widespread needs for creating low pressure ambient in various industries make vacuum systems have different research and industrial applications. One of these applications is in cooling system of Rankine power cycle. In this case, the performance of the vacuum system has a direct and significant effect on the cooling performance of the condenser and consequently, power production of the steam turbine. Also, a considerable part of deration in thermal power plants industry is due to the thermal deration of the cooling systems. This is mostly because of malfunction of the condenser due to ambient temperature rise. Therefore, by providing suitable solutions to improve the efficiency... 

In recent years, there has been the extensive researches on energy and water efficiency due to the increasing stress on these resources. Therefore, the water-energy nexus in large industries, especially power plants, has become very important. In the present study, the water and energy nexus has been analyzed using energy analysis tools, exergy, economic and environmental in a combined cycle power plant. The nexus are observed in the boiler blow-downs, leakage of steam traps, cooling of the air entering the compressor and injection of steam into the combustion chamber, which have been studied in different scenarios to improve water and energy consumption and reduce environmental impact. In... 

Considering the supply and demand market of natural gas, methanol, propylene and ethylene and the propylene value chain, it is expected that the design of the propylene production process from methanol produced from natural gas and its implementation in Iran country can significantly flourish the production of polypropylene, acrylonitrile and Etc. On the other hand, with the industrialization of this process, the uncontrolled export of methanol from Iran to countries such as China and the devaluation of methanol will be prevented. In this report, the process of producing synthetic gas from natural gas using autothermal reactor and heat exchange reforming, separation and storage of carbon... 

Synthesis gas (H2, CO) is widely used in chemical and petrochemical industries, utilized for methanol and ammonia production. Hydrogen is the main component of syngas which is considered as an appropriate alternative for fossil fuels. Catalytic steam reforming is one of the most common and economical pathway for syngas production. Light hydrocarbons such as propane which can easily be transported, stored and distributed, is a promising feed candidate for steam reforming. Catalyst deactivation along with low stability resulting from carbon formation and sintering is one of the main crucial problems in this process, leading to much research on the preparation of stable and coke resistant... 

Methane steam reforming (MSR) is an assuring reaction using steam to produce H2 as clean energy over a nickel-based catalyst. We synthesized monometallic NiMgAl2O4 and bimetallic NiCoMgAl2O4 catalysts in a two-step combustion method using urea, glycine, and sucrose, as fuel. BET-BJH, XRD, TGA, TPR, FESEM, and EDX-mapping characterized surface area, porosity, morphology, crystalline structure, and metal-support interaction behavior. The products exhibited well-structured, simple MgAl2O4 spinel and NiO without NiAl2O4, in both specimens. The MSR evaluation tests at 750℃ under atmospheric pressure, CH4: H2O feed ratio of 1:1.6 showed the bimetallic catalyst has the highest conversion (99.30%)... 

Todays, heat recovery steam generator (HRSG) systems are used extensively in combined power plant cycles (consisting of Rankine cycles and Brighton gas cycle) to maximize their efficiencies. The role of HRSG is essential in providing additional energy needed in the steam cycle part. The HRSG has many pipes or harps. They recover the heat from the incoming gas from the gas turbine outlet, which may be boosted up by the duct burner unit. The main challenge in simulating heat recovery units such as tube bundles is to provide ultra-large and cost-efficient grids. In such situations, alternative models are used to simplify the simulation of the steam generator in full scale, including the... 

Due to the increasing cost of energy, we want in this study to increase energy efficiency and reduce waste of system energy. Oil, gas and petrochemical sector is a widespeard part in Iran, so the study of energy systems in the industry have a paramount importance. The study focused on the Tehran refinery steam and power systems, seeking the most economical system of power and steam for the Tehran refinery. To achieve this goal, with the help of simulation of power and steam system for Tehran refinery with Aspen Utility software, a superstructure obtained. Then, using a sensitivity analysis, we were able to achieve economic arrangment of utility system. In this study by increasing the...