Sharif Digital Repository

Performance of Polymer Electrolyte Membrane Fuel Cells (PEMFC) at high current densities is limited to transport of reactants and products. Also at high currents, large amounts of water are gener-ated due to electrochemical reactions. Due to low temperature of PEMFC, some of the steam condenses. The amount of water existing in a PEMFC influences its performance. Shortage of water adversely af-fects cell performance by drying out the membrane. On the other hand, an excessive amount of water blocks pores of porous medium and transport of fuel becomes difficult.
In order to predict flooding and its effects on the PEMFC performance, development of a two-phase flow model is necessary. In this... 

Asphaltene, the heaviest and most polarizable fraction of crude oil, has a potential to precipitate, deposit and plug pipelines, causing considerable production costs. The main objective of this study is to contribute to the thermodynamic and transport modeling of asphaltene in order to predict its precipitation, segregation and deposition. Potential calculation of some thermophysical properties of asphaltene is also explored. Predicting the flow assurance issues caused by asphaltene requires the ability to model the phase behavior of asphaltene as a function of pressure, temperature and composition. It has been previously demonstrated that the Perturbed Chain form of Statistical Association... 

Isolated electric energy systems are often needed to supply 3 kind of electric loads. This could be caused due to geographic isolation, the necessity of load mobility, demanded values of voltage and current that are not compatible with the local networks. This makes the design and construction of stand-alone energy systems a must. Because of sustainability concerns and enviromental pollution avoidance, Modern designs are being pushed towards cleaner energies and technologies. Polymer electrolyte membrane type fuel cells are among the new technologies that are being considered as a good alternative to the traditional power sources used for stand-alone energy systems. Although the basic... 

The aim of the proposed thesis is to devise a method of passage-way identification and crossing control of an experimental swarm robot. In the previous works done in the Sharif University of Technology, The main focus was on the collective behaviours than can be emeged from a swarm robot. Collective behaviours are such a primitive behaviours that are combined in order to lead to a real mission. In this investigation, the main focus is on the design of a mission. In this way, by combining the aggregation-divegance, chain formation, leader following and wall following collective behaviours, the desired is fulfilled. The algorithms is so that in the first stage, the agents of the swarm... 

In this research, the aim is to investigate the use of data assimilation method for better reservoir model updating in the reservoir management. In addition, multi-objective optimization concept is studied for the production optimization. The application of these methods is applied for reservoir management in the naturally fractured reservoirs. To update the reservoir, ensemble based methods, especially ensemble Kalman filter and ensemble smoother, are used. To tackle the challenges encountered with these methods, modifications are proposed to obtain a better history matching and more accurate reservoir characterization. The proposed framework for history matching is implemented for the... 

In this thesis non-ideal behavior of fluids and its effects on hydrodynamic and mass transfer in multiphase flow is studied. A numerical framework has been proposed to model the interacting effects of mixture non-ideality and mass transfer on hydrodynamics of a multiphase system using CFD methods. Using the numerical framework mass and momentum transfer in a system was simulated. The system consists of a cylindrical vessel filled with vapor and liquid hydrocarbons which selected as the benchmark. The liquid hydrocarbon is chosen to be pure Octane and the hydrocarbon in the gas phase is assumed to be Propane. Due to operating condition (T=323 K, P =445 kpa) the behavior of fluid is non-ideal... 

Synthesis gas to light olefin reactions especially propylene production is one of the important path for clean fuel production in gas conversion processes. The object of this study is to define true kinetic model of process first step (e.g. Synthesis gas to light Olefins). For that, kinetic model for Co/Mn/TiO2 catalyst, which has the best conversion and selectivity for propylene, has been developed. Kinetic reaction parameters were measured by kinetic modeling in (220-300)0C temperature , (1-5)bar pressure , H2/CO=(1:3) and (450-600)hr-1 space velocity .After studying with significant models ,the best fitting can obtained with "KPCO P 1/2H2/(1+aPco+bPH2 1/2)2"equation. Later to... 

In the present work, a comprehensive economic, environmental and exergy analysis and multi-objective optimization for gas sweetening plant are provided and the interaction between decision variables in these criterions is discussed. In the first part, potentials of three environmental features (global warming, acid rain, smog formation) of the operational plant are quantified and normalized using life cycle assessment (LCA) for both process waste and utility environmental impacts.Acid rain index is determined as the most important environmental impactindex in this unit. By choosing proper decision variables based on sensitivity analysis, LCA and EA results, optimization is performed to... 

Digital analysis of reservoir rocks prepares a powerful tool in the field of porous media studies and provides appropriate information of single / multiphase flows by performing numerical simulations on porous media images. In order to access the necessary tools to benefit from digital rock analysis and characterization, we need accessing the porous media images, the geometric distribution and the spatial distribution of pores and grains through imaging or reconstruction methods. Porous media reconstruction methods are known as an alternative to imaging techniques. In addition, reconstruction methods have the ability to fix problems and imperfections associated with imaging, such as... 

The industrial paradigm shift toward intelligent and sustainable management stimulates policymakers to leverage artificial intelligence for the decentralized planning of chemical industries with energy networks. By doing so, this work firstly presents a simulation framework to investigate the rigorous transient behavior of integrated systems comprising natural gas and power transmission networks, along with a chemical plant whose feedstock is natural gas. This framework entails dynamic models for the gas transmission network and the SynGas plant, and a continuous-time AC-power flow formulation with dispatchable loads. It addresses the following key challenges: (i) analyzing energy and... 

Management decisions, enhanced oil recovery, and reservoir development plans in petroleum industries are based on predictions by reservoir simulation. Due to uncertainties in model parameters or engineering assumptions, the simulation results are not accurate, while they are correct. For more accurate estimation of unknown production quantities, it is required to characterize the unknown parameters and its uncertainty. By using static data alone the result of characterization is unreliable and unsure, therefore dynamic data use practically. In reservoir engineering literature, this is called “History Matching”.The ensemble Kalman filter is an optimal recursive data processing algorithm based... 

The main objective of the present work is to achieve green design of a methanol plant by using life cycle process design (LCPD) and multi-objective optimization. As a starting point, simulation of Lurgi’s combined reforming process as a conventional reference methanol case (RMC) was performed in order to obtain its operational and kinetic parameters as well as its environmental impacts. The environmental concerns were calculated using one of the modern environmental impact assessment methods, i.e. life cycle assessment (LCA). To perform life cycle assessment of RMC, methanol production plant as well as its auxiliary units should be considered. The auxiliary units in the RMC include cryogenic... 

Hydrocarbon reservoirs development and management is based on their dynamic models. To encounter various types of error during model building, model parameters are adjusted to produce reservoir historical data by assimilation (history matching) of reservoir production or 4D seismic data. Among the existing sequential methods for automatic history matching, ensemble Kalman filter and its variants have displayed promising results. The innovations of this thesis for ensemble Kalman filter (EnKF) are presented into three major orients; these includes adaptive localization/regularization, characterization of original PUNQ test model and characterization of channelized reservoir.
To mitigate... 

Many spacecrafts and satellites have long flexible components, the most common ones are the satellites with flexible solar panels, which are used to provide the satellite energy. The governing equations of the satellite rigid motion along with the solar panels vibrations are the combination of the coupled partial and ordinary differential equations. Various reasons, such as the satellite maneuvers and the external disturbances, cause the vibration of panels. Due to the dependence between the governing equations of the satellite rigid motion and the flexible components vibrations, these vibrations affect the satellite rigid dynamics and the control aims; therefore, in addition to the... 

Natural tissues of body consist of Extra Cellular Matrix (ECM) and cells. Scaffold produces a temporary matrix for cells and facilitates oxygen and nutrients transport which enhances tissue regeneration. Therefore, attempts in regeneration of tissues and organs by scaffolds attracted great interest in today’s researchs. Choosing scaffold fabrication method and its polymer type, play a key role in scaffold specifications as they determine scaffold properties. In this project electrospinning was chosen as the scaffold fabrication method which is because of the unique properties of scaffolds fabricated by this method and also its ability in producing micro and nano fibers. At first set of... 

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... 

The gas flow field geometry influences the transport phenomena inside PEMFCs and hence affecting their overall performance. Radial force and secondary flows resulting from curvature of the spiral channels in PEMFCs can improve mass transport limits and so does to their overall performance. Studying the effects of curvature of spiral channels on fuel cell performance and comparing them with similar designs is the aim of this thesis. The geometries are generated using concentric Archimedes’ spirals and categorized as axial or radial depending on the direction of the vector perpendicular to their MEA . Each category has five geometries which are the result of branching the main channel into...