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Investigation and Simulation of Overcooling Transients of The Bushehr's VVER-1000 Nuclear Power Plant with RELAP5/MOD3.3
, M.Sc. Thesis Sharif University of Technology ; Ghofrani, Mohammad Bagher (Supervisor)
Abstract
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...
Microwave-Assisted Coke Resistance and Mesoporous Ni-Co Catalyst in two Steps for Methane Steam Reforming
, M.Sc. Thesis Sharif University of Technology ; Sadrnezhad, Khatiboleslam (Supervisor)
Abstract
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%)...
Developing Advanced Models to Simply Simulate the HRSG of Class F Turbine in Full Scale
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
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...
Dynamic Modeling of Top-Fired Steam Methane Reforming Furnaces
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Fathollah (Supervisor) ; Vafa, Ehsan (Supervisor)
Abstract
CFD models are accurate but time-consuming for simulation and optimization of steam methane reformer and controlling the tube wall temperature, and syngas production rate and unsuitable for online optimization. Empirical data-driven models are less accurate when there are wide variations in operating conditions. The physics-based model presented in this thesis overcomes these limitations. In this model, the furnace side and the process side are divided into zones with uniform temperature and composition, and for each zone, mass, energy and momentum balances are derived. Radiative heat transfer modeling and calculation of exchange areas are accomplished with the zone method. The system of...
Using sliding mode control to adjust drum level of a boiler unit with time varying parameters
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis ; Vol. 5 , 2010 , pp. 29-33 ; ISBN: 9780791849194 ; Bakhtiari-Nejad, F ; Saffar-Avval, M ; Alasty, A ; Sharif University of Technology
Abstract
Stable control of water level of drum is of great importance for economic operation of power plant steam generator systems. In this paper, a linear model of the boiler unit with time varying parameters is used for simulation. Two transfer functions between drum water level (output variable) and feed-water and steam mass rates (input variables) are considered. Variation of model parameters may be arisen from disturbances affecting water level of drum, model uncertainties and parameter mismatch due to the variant operating conditions. To achieve a perfect tracking of the desired drum water level, two sliding mode controllers are designed separately. Results show that the designed controllers...
Greenhouse gas emission measurement and economic analysis of Iran natural gas fired power plants
, Article Energy Policy ; Volume 60 , 2013 , Pages 200-207 ; 03014215 (ISSN) ; Kiyoumarsioskouei, A ; Asheri, M. H ; Naemi, S ; Shahsavari Alavije, H ; Basirat Tabrizi, H ; Sharif University of Technology
2013
Abstract
This study attempts to examine the natural gas fired power plants in Iran. The required data from natural gas fired power plants were gathered during 2008. The characteristics of thirty two gas turbine power plants and twenty steam power plants have been measured. Their emission factor values were then compared with the standards of Energy Protection Agency, Euro Union and World Bank. Emission factors of gas turbine and steam power plants show that gas turbine power plants have a better performance than steam power plants. For economic analysis, fuel consumption and environmental damages caused by the emitted pollutants are considered as cost functions; and electricity sales revenue are...
Exergy, economic, and environmental analysis of a PEM fuel cell power system to meet electrical and thermal energy needs of residential buildings
, Article Journal of Fuel Cell Science and Technology ; Volume 9, Issue 5 , 2012 ; 1550624X (ISSN) ; Ehyaei, M. A ; Mozafari, A ; Atabi, F ; Hajidavalloo, E ; Shalbaf, S ; Sharif University of Technology
ASME
2012
Abstract
In this paper, a Polymer Electrolyte Membrane (PEM) fuel cell power system including burner, steam reformer, heat exchanger, and water heater has been considered. A PEM fuel cell system is designed to meet the electrical, domestic hot water, heating, and cooling loads of a residential building located in Tehran. Operating conditions of the system with consideration of the electricity cost has been studied. The cost includes social cost of the environmental pollutants (e.g. CO 2, CO and NO). The results show that the maximum energy needs of the building can be met by 12 fuel cell stacks with nominal capacity of 8.5 kW. Annual average electricity cost of thissystem is equal to 0.39 US$/kWh and...
Using sliding mode control to adjust drum level of a boiler unit with time varying parameters
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010, Istanbul ; Volume 5 , 2010 , Pages 29-33 ; 9780791849194 (ISBN) ; Bakhtiari Nejad, F ; Saffar Avval, M ; Alasty, A
2010
Abstract
Stable control of water level of drum is of great importance for economic operation of power plant steam generator systems. In this paper, a linear model of the boiler unit with time varying parameters is used for simulation. Two transfer functions between drum water level (output variable) and feed-water and steam mass rates (input variables) are considered. Variation of model parameters may be arisen from disturbances affecting water level of drum, model uncertainties and parameter mismatch due to the variant operating conditions. To achieve a perfect tracking of the desired drum water level, two sliding mode controllers are designed separately. Results show that the designed controllers...
Numerical optimization and manufacturing of the impeller of a centrifugal compressor by variation of splitter blades
, Article ASME Turbo Expo 2016, Turbomachinery Technical Conference and Exposition, 13 June 2016 through 17 June 2016 ; Volume 8 , 2016 ; 9780791849866 (ISBN) ; Hajilouy Benisi, A ; Durali, M ; International Gas Turbine Institute ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
Abstract
Design and optimization of centrifugal compressors, based on main blades configuration of impeller have been vastly discussed in open literature, but less researches have addressed splitters. In this research, the impeller of a commercial turbocharger compressor is investigated. Here, profiles of main blades are not changed while the effect of changing the configuration of splitters is studied. An optimization study is performed to find the best configuration using genetic algorithm over a complete operating curve of the compressor. CFD codes with experimental support are used to predict the compressor performance. Quantumetric tests beside destructive analysis of two impellers are...
Performance of a nickel-alumina catalytic layer for simultaneous production and purification of hydrogen in a tubular membrane reactor
, Article RSC Advances ; Volume 6, Issue 79 , 2016 , Pages 75686-75692 ; 20462069 (ISSN) ; Towfighi, J ; Zamaniyan, A ; Ganji Babakhani, E ; Heidari, M ; Sharif University of Technology
Royal Society of Chemistry
2016
Abstract
A catalytic membrane reactor was synthesized by coating a 4-5 micron thick Ni/γ-Al2O3 layer on top of a hydrogen selective SiO2/Al2O3 composite membrane using a sol-gel method. Mercury intrusion and BET analysis indicated a uniform size distribution with an average pore size of 285 nm and average surface area of 279 m2 g-1. Single-component permeation tests were carried out for H2, CH4 and CO2 in the temperature range of 650-800 °C and the results showed the same permeance and selectivity values for hydrogen as the composite membrane without a catalytic layer. Performance of the catalytic membrane was evaluated by using as a membrane reactor for the methane steam reforming reaction with a...
Determination of the extended Drucker-Prager parameters using the surrogate-based optimization method for polypropylene nanocomposites
, Article Journal of Strain Analysis for Engineering Design ; Volume 51, Issue 3 , 2016 , Pages 220-232 ; 03093247 (ISSN) ; Majzoobi, G. H ; Bagheri, R ; Sharif University of Technology
SAGE Publications Ltd
2016
Abstract
In this article, a new method is proposed to identify the constants of the extended Drucker-Prager yield surface for polypropylene nanocomposites. The method is based on optimizing the difference between the numerical and the experimental results of a three-point bending test. The test specimens are made of polypropylene/nanoclay and polypropylene/nano-calcium carbonate nanocomposites with different nanoparticles content. Moreover, the effect of composite filler content on the extended Drucker-Prager constants of polypropylene, as the composite matrix, is investigated. Inasmuch as numerical simulation is usually very time-consuming and highly nonlinear, a surrogate-based model with radial...
Radiative heat transfer modeling in numerical simulation of a heavy duty steam generator
, Article 54th AIAA Aerospace Sciences Meeting, 2016, 4 January 2016 through 8 January 2016 ; 2016 ; 9781624103933 (ISBN) ; Abrar, B ; Barezban, M. B ; Schneider, G.E ; Shamsaei, Y ; Nematollahi, M ; Sharif Universty of Technology
American Institute of Aeronautics and Astronautics Inc, AIAA
Abstract
The proper modeling of radiation is of great importance in numerical simulation of combustion processes. A simple gray weighted-sum-of-gray-gases (WSGG) model has been intensively used in CFD simulations of industrial combustion applications, mainly because of its low computational costs. However, the gray assumption is far from the real behavior of non-gray combustion gases. This could consequently affect the accuracy of temperature field and heat flux distribution predictions. On the other hand, modern non-gray global radiation models such as the standard spectral line-based weighted-sum-od-gray-gases (SLW) model are still computationally expensive for many engineering purposes. To...
Examination of a novel solar still equipped with evacuated tube collectors and thermoelectric modules
, Article Desalination ; Volume 382 , 2016 , Pages 21-27 ; 00119164 (ISSN) ; Shahmohamadi, M ; Faegh, M ; Sadrhosseini, H ; Sharif University of Technology
Elsevier
2016
Abstract
In this article, a novel solar still which is equipped with thermoelectric modules to utilize the heat of vapor condensation is experimentally investigated. The use of thermoelectric modules as devices for generating electricity from the temperature difference between two environments (hot vapor steam and cold ambient air) as well as taking outstanding advantages of evacuated tubes as collectors with high performances in adverse climatic conditions, led to utilizing of the energy dissipated due to vapor condensation and a considerable increase in the performance of the system. The effect of using the generated electricity to operate a small propeller fan for inducing forced convection was...
Influence of interfacial adhesion on the damage tolerance of Al6061/SiCp laminated composites
, Article Ceramics International ; Volume 43, Issue 2 , 2017 , Pages 2632-2643 ; 02728842 (ISSN) ; Pouraliakbar, H ; Jandaghi, M. R ; Bagheri, R ; Seyed Reihani, S. M ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
In this study, lamination as extrinsic mechanism was considered to enhance damage tolerance of three-layer Al6061-5%vol. SiCp/Al1050/Al6061-5%vol. SiCp composites. To fabricate laminates of dissimilar interfacial adhesion, different rolling strains were applied during hot roll-bonding. The discrepancy in interfacial strength of laminates was examined by shear test while toughness values were studied using three-point bending test. It was revealed that both interfacial adhesion and damage tolerance were influenced by rolling strain. Interfacial bonding played the major role in the energy absorption during fracture which was quantified as initiation, propagation and total toughness. The...
Profit-based unit commitment of integrated CHP-thermal-heat only units in energy and spinning reserve markets with considerations for environmental CO2 emission cost and valve-point effects
, Article Energy ; Volume 133 , 2017 , Pages 621-635 ; 03605442 (ISSN) ; Ardehali, M. M ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
For the purposes of lowering environmental emission cost and increasing economic profit, energy efficient combined heat and power (CHP) units can be integrated with conventional separate heat and power production units to meet heat and power demands. The goal of this study is to develop and examine a novel heuristic and deterministic optimization algorithm for solving the profit-based unit commitment (PBUC) problem for a generation company with integrated CHP-thermal-heat only system for (i) satisfying demands for heat and power, (ii) selling spinning reserve for power, (iii) reducing environmental CO2 emission cost, and (iv) accounting for valve-point effects for steam turbines. For...
Failure analysis of bolt connections in fired heater of a petrochemical unit
, Article Engineering Failure Analysis ; Volume 92 , 2018 , Pages 327-342 ; 13506307 (ISSN) ; Chamani, M ; Reza Kashyzadeh, K ; Mostafazade, A ; Mahmoudi, A. H ; Afshin, H ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
The main function of a fired heater in a petrochemical site is to produce supersaturated steam. Due to extremely difficult working conditions and high temperatures, there is a very high probability of failures in different parts of a fired heater. In the fired heater under study, tube guides are frequently damaged due to malfunctions and fractures in bolt connections. To investigate the nature of such fractures, Computational Fluid Dynamics (CFD), Finite Element (FE) method, Charpy impact test and fractography were used. To obtain the temperature of various components of the fired heater, a CFD analysis was carried out by considering the combustion process and modeling the central and side...
Preparation and characterization of starch-based composite films reinforced by cellulose nanofibers
, Article International Journal of Biological Macromolecules ; Volume 116 , 2018 , Pages 272-280 ; 01418130 (ISSN) ; Keley, M ; Biazar, E ; Sharif University of Technology
Elsevier B.V
2018
Abstract
The current study deals with the preparation and characterization of polysaccharide-based biocomposite films acquired by the incorporation of cellulose nanofiber within glycerol plasticized matrix formed by starch. The application of starch-based films is limited due to highly hydrophilic nature and poor mechanical properties. These problems are solved by forming a nanocomposite of thermoplastic starch (TPS) as matrix and cellulose nanofiber (CNF) as reinforcement. CNF is successfully prepared from short henequen fibers which consist of almost 60% cellulose by a chemo-mechanical process. TPS/CNF composite films are prepared by the polymer solution casting method, and their characterizations...
Experimental study of dynamic imbibition during water flooding of naturally fractured reservoirs
, Article Journal of Petroleum Science and Engineering ; Volume 174 , 2019 , Pages 1-13 ; 09204105 (ISSN) ; Masihi, M ; Mirzaei Paiaman, A ; Hamidpour, E ; Sharif University of Technology
Elsevier B.V
2019
Abstract
Capillary imbibition is an important recovery mechanism in naturally fractured reservoirs when water-filled fractures surround water-wet matrix blocks. A large amount of studies of imbibition process is simply total or partial immersion of nonwetting phase saturated rock in aqueous wetting phase. However, water advance in fractures during water flooding or water encroachment from an active aquifer introduces time dependent boundary conditions where invariant exposure of rock surface to water is not representative. In this work, a laboratory simulated matrix-fracture system was used to investigate different aspects of imbibition in the presence of fracture fluid flow (namely dynamic...
CFD modeling of gasification process in tapered fluidized bed gasifier
, Article Energy ; Volume 191 , 2020 ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
This article presents a two-dimensional simulation of the coal gasification in tapered fluidized bed gasifier. The effects of tapered angle, gasifier temperature, velocity of gasifying agent, and steam-to-air ratio on the gas compositions, lower heating value (LHV), and higher heating value (HHV) were examined. In order to find the appropriate operating conditions of coal gasification, carbon conversion efficiency (CCE) and cold gas efficiency (CGE) were also explored. It was found that with an increase of the gasifier temperature, CCE and CGE of the tapered gasifier diminishes. Increasing tapered angle results in a decrease of the LHV and HHV of the gas products, whereas the CCE of...
Thermal performance assessment of an evaporative condenser-based combined heat pump and humidification-dehumidification desalination system
, Article Desalination ; Volume 496 , 2020 ; Shafii, M. B ; Sharif University of Technology
Elsevier B.V
2020
Abstract
A new design for heat pump integrated humidification-dehumidification (HDH-HP) desalination cycles was proposed in the current experimental study. An evaporative condenser was designed and fabricated instead of a separate humidifier, heater, and air/water-cooled condensers find in previous HDH-HP systems. Meanwhile, the air dehumidification process in this work directly occurred inside the heat pump evaporator. The effect of several operating parameters such as ambient wet-bulb temperature, spraying saline water and airflow rates, compressor speed, superheat, and evaporator saturation temperature control modes of the electronic expansion valve (EEV) on freshwater production and GOR were...