Sharif Digital Repository

In the proton exchange membrane fuel cells (PEM, the produced water would be divided into two phases of vapor and liquid. distribution of both liquid and vapor phases in different cell layers affects the performance, the efficiency and the life of a fuel cell significantly. Moreover, Nano pores of the cathode catalyst layer are involved with some phenomena such as electrochemical reaction kinetics, heat and mass transfer and interface phase change. One of the most important problems in the performance of fuel cells is distribution of liquid water in the porous areas. Water flooding in fuel cells causes to delay in oxygen transport to active sites in the catalyst layer because the pores of... 

Hydrodynamics plays a crucial role in defining the performance of fluidized beds. The numerical simulation of fluidized bed is very important in the prediction of its behaviour. From this point of view, in the present study a dynamic two dimensioanl model is developed for the modeling of regenerator system of a UOP fluid catalytic cracking (FCC) unit of Abadan refinery with a high-efficiency regenerator. Of the various modeling and simulation techniques, computational fluid dynamics (CFD) is employed in this thesis. Effects of gas velocity, the transient local solid volume fraction, pressure drop for gas and solid phase, solid holdup distribution and solid circulation pattern have been... 

Polycrystalline materials are solids that are composed of many crystallites of varying size and orientation called “Grain”. As the grain size reduces to the values below 100nm, the overall material properties are remarkably changed, and thus the resulting nanocrystalline materials have provided much better engineering properties at the same chemical composition compared to the microcrystalline. The main objective of the present study is to synthesize a nanocrystalline (22nm-25nm) coating based on Nickel over the yellow-brass plates. To do this, an electroplating technique in a modified Watts bath is employed in which the current density and stirring speed varied between 3 to 9.5 Ampere per... 

In this project, nonocrystalline zinc coatings with grain sizes within the range of 22-63 nanometers were produced on yellow-brass plates by electroplating in an acidic chloride bath in the presence and absence of additive has been investigated.current densities and bath stirring speeds change from 2 to 6 A/dm2 and 0 to 400 rpm respectively.To determine crystallite size, X-ray diffraction technique (XRD) was utilized;it was found that the use of additive has effectively refined the grain size and optimum current density is 3 A/dm2 to reach this objective.. it was observed that grain size increased continuously with increase in bath stirring speed. The results coming from XRD tests were... 

A two-dimensional, two-phase, nonisothermal model was developed in this work to investigate the water transport characteristic and water distribution in a direct methanol fuel cell (DMFC). Emphasis is placed on exploring the water distribution in different layers of DMF. The water and methanol crossover through the membrane were considered with the effect of diffusion, electro-osmotic drag, and convection. Governing equations including the prton and electron transport, continuity, momentum, species transport for methanol, water, and gases species, and the auxiliary equations are coupled to determine the output parameters. These parameters are the concentration distribution of the species,... 

Platinum is one of the most used catalysts in refining and petrochemical industries. Also, Platinum uses in other industries like automobile catalytic convertor. As respect to importance of Platinum in these industries, growth of its consumption in recent decades and its very high price, recovery of Platinum is essential. Hence, many of various methods including hydro-metallurgy are applied. In despite of these wide spreading experimental investigations, due to low information about the reactions and the nature of reaction products, a few investigations were done on kinetics of Platinum recovery. A new method that used iodine solution to extract Platinum from spent reforming catalysts was... 

In this study, deactivation of Midrex reforming catalysts is evaluated kinetically by 3.5-year data of Mobarakeh Steel Company direct reduction site. The variation of Midrex catalyst’s structure is characterized by XRD and BET test. Two deactivation mechanism are characterized, methane cracking carbone deposition and sintering. The project results demonstrate that victorious mechanism is carbon deposition. The methane cracking carbone cause layer by layer deactivation of catalyst during 5.5 months. Although, XRD and BET showed pore volume and radius reduction and Ni crystal increasing, approximated constant activity of catalyst were approved by kinetic evaluation  

In this project, a model which had been suggested for a lithium battery is used with the assumption of using C.N.T instead of activated carbon for the cathode. This battery include lithium foil, C.N.T and solution as anode, cathode and electrolyte. The electrolyte solution consist of lithium salt and a separator. The mathematical solving of the model consisted of using two CPM and DFM methods. In DFM method, a concentration gradient was considered as the driving force for diffusion and in the CPM method chemical potential as the driving force. Furthermore CPM method considered energy interaction between ions. Changing physical parameters of cathode and modification of model parameters... 

Because of the importance of purification units at the refineries, in this research the process of sulfur removing compounds from light naphtha product with 1 ppm concentration by adsorption method in a fixed bed tower was simulated by COMSOL Multiphysics software. In this work, simulation was done using two macro and micro perspectives. In the Macro-scale mass transfer takes place between the spherical particles of catalyst and in the micro-scale mass transfer takes place within the spherical particles and these two scales were coupled together by reaction rate variable. In Macro-scale one-dimensional and two-dimensional geometry were considered for model. Naturally, the result of the... 

In this study, the effect of nano-structure mesoporous supports on the performance of the nickel catalysts in the combined reforming process was investigated. In the first part, magnesium aluminate spinel was prepared using a sol-gel method and employed as a catalyst support for the preparation of nickel catalysts with various nickel contents. The samples were characterized using BET, XRD, TPR, TPO, CO chemisorption and SEM techniques. The results showed that increasing the nickel content up to 7.5 wt.% improved the catalytic activity, but further increase in nickel content decreased the activity due to the decrease in the nickel dispersion. The catalysts except of the sample with 2.5 wt.%... 

Polymer electrolytes are most frequently used electrolytes especially in lithium ion batteries. The gel-polymer and polymer-ceramic electrolytes were synthesized using DMA plasticizer, LiClO4, and SiO2 ceramic Nano fillers through coating method. EIS, FTIR, XRD, SEM, and TGA analyses were carried out on electrolytes. The optimum amount of perchlorate and polymer was obtained 0.5 M and 5% w/w, respectively. Also, the optimum amount of silica was obtained 2% w/w. the optimizations were carried out suing conductometry. The EIS analysis showed the ionic conductance of gel-polymer 1.8 mS.cm-1 while that of ceramic-polymer was obtained 2.8 mS.cm-1  

Catalytic reforming of naphtha is an important process to convert of low-octane number naphtha into high-octane number gasoline. Deactivation of catalysts, is the major problem for this process. In this study, catalytic reforming unit of Tabriz oil refinery investigated, and Smith’s kinetic model used for modeling. Also, several models presented for activity of catalysts. To find the parameters of presented models, the difference between the calculated and experimental values of outlet temperatures of each bed and aromatics, paraffin and naphthene yields simultaneously must be minimized. Using Genetic Algorithm Toolbox in Matlab software, optimization was performed and results indicated that... 

In this project, nonocrystalline nickel coatings with grain sizes within the range of 9-27 nanometers were produced on yellow-brass plates by electroplating in a modified Watts bath applying current densities from 2 to 6 A/dm2 and bath stirring speeds from 0 to 400 rpm. To determine crystallite size, X-ray diffraction technique (XRD) was utilized; it was observed that grain size declined continuously with increase in current density and then in bath stirring speed. The experimental results coming from XRD tests were compared with a theoretical model in order to verify their reliability; the obtained curve indicated a good correspondence between the experimental data and the theoretical... 

Nowadays catalytic reforming of naphtha is one of the most important parts of the refining process. The catalyst of this process is mostly Pt-Re on the γ-alumina support. The major cause of deactivation is coke deposition and blockage of the pores as a result. Meanwhile, modeling of the process and the deactivation of catalyst would help refining industries to achieve higher yields. In this study industrial data of the catalytic reforming unit #2 in Isfahan Refinery Plant were used to model the process, optimized parameters have been calculated and the best contribution of the catalyst among the four reactors was presented. Then with using a deactivation function the whole coking... 

Fuel cells provide a clean mechanism of energy conversion and they have been given due consideration in recent years. Polymer membrane fuel cells have particularly been considered because of a wide range of their application and their portability. The industrial application of this type of fuel cells is spreading rapidly in recent years. Therefore, optimal design of such technologies of fuel cells may accelerate their industrial application. Bipolar/ end plates are detrimental to high efficiency and power density in fuel cells. Appropriate design of bipolar plates with suitable distribution of gas and the least pressure drop could provide the best possible outlet of reaction... 

Fuel Cell with Polymer membrane uses a reaction with Hydrogen and Oxygen as reactants to produce electricity. As the product of this reaction is water, this fuel cell produce clean energy. But if the produced water accumulates it can cause problems for fuel cell which can lead to complete failed of fuel cell. On the other hand water shortage in PEM fuel cell also can cause problems. So we need to have continues water management inside of PEM fuel cell. For this sake having knowledge about water inside of PEM fuel cell and specially the Gas Diffusion Layer which is the layer with responsibly to help the fuel cell to manage the water, is necessary. One of the ways for gaining that knowledge... 

Fossil fuel are energy resources in decline. In recent years, fuel cell have become as a source of energy to replace conventional systems .Among the various types of fuel cells, PEMFCs (proton exchange membrane fuel cells) possess a series of highly advantageous features such as a low-operating temperature, sustained operation at high-current density, low weight, compactness, potential for low cost and volume, long stack life, fast start-ups and suitability for discontinuous operation. Water management is one of the most critical and challenging problems. There is a delicate balance between the membrane hydration and avoiding cathode from flooding. Cathode flooding occurs when the water... 

The main objective of this research is to experimentally evaluate thermal behavior of commercially available rechargeable Li-ion batteries based on minimum measurements on main battery parameters and then develop experimental based models to investigate their thermal behavior. Li-ion batteries with Graphit anodes and Li(Ni0.8¬Co0.15Al0.05)O2 cathodes will be used for this purpose. Voltage and temperature developments during cycling under various currents at controlled ambient temperatures are measured by battery tester. Measurements show that temperature evolutions demonstrate falls and rises at specific State-of-Charge (SoC) of the battery during cycling and therefore some heat consumers... 

well known metal-free nanostructure carbon-based catalyst, mesoporous graphitic carbon nitride, with diverse morphologies were synthesized by using ethylendiamine/carbontetrachloride as a precursor, SBA-15 and SBA-15 nanorod as hard templates. We have investigated morphology effect on the catalytic performance. The catalysts were characterized by means of low angle and wide angle XRD, BET, FT-IR, CHNOS, FE-SEM analysis. Because of high surface area, pore volume and high nitrogen content, which acts as lewis basic site, for the first time, carbon nitride is chosen for selective catalytic oxidation of hydrogen sulfide to sulfure. Reaction was taken place in a fixed-bed reactor and at... 

There are many archeological sites, historic building monuments and inscriptions in Iran and other countries in the world which have been damaged by environmental as well as biological causes. Lichens are one of the biological causes which, through their growth, bring about change and damage to the stones. Different methods, each of which has both advantages and disadvantages, have been used in order to deal with the problem. Since there are many historic buildings in our country which have been damaged by different biological causes including the lichens, doing a research on the topic seems to be quite significant and necessary. The Persepolis is among one of the most important historic...