توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱Enhancement of Methanol Production in a Single–Type Reactor with CO Injection
نویسنده(ها): ، ،
اطلاعات انتشار: ششمین کنگره بین المللی مهندسی شیمی، سال
تعداد صفحات: ۷
Dynamic simulation of a single–type industrial methanol reactor with CO–rich feed that supplied from the reactor output, has been studied in the presence of long term catalyst deactivation. In this work, the one–dimensional heterogeneous dynamic model has been considered. A single–type methanol reactor is basically a vertical shell and tube heat exchanger. The catalyst is packed in vertical tubes and surrounded by the boiling water. The methanol synthesis reactions are carried out over commercial CuO\ZnO\Al2O3 catalyst. The heat of exothermic reactions is transferred to the boiling water and steam is produced. We investigated the performance of rector with CO injection to feed entrance and compared productm and reactant mole fraction profiles of aforesaid reactor with that of conventional single type (CMR) and membrane methanol reactor (MMR). The simulation results represent 14.24% and 22.93% enhancement in the yield of methanol production in comparison with MMR and CMR, respectively while 5% CO was injected into the 95% of feed. On the other hand, CO is an important cause of pollution and a hazardous material in many industrial processes which must be removed and this method is a suitable method for this case.<\div>

۲Assessment of Different Turbulence Models and Kinetic Mechanisms for Simulation of Jet in Hot Coflow Flames
نویسنده(ها): ، ،
اطلاعات انتشار: سومین کنفرانس ملی کاربرد CFD در صنایع شیمیایی، سال
تعداد صفحات: ۱۱
In this paper, flameless combustion in a lab–scale jet in hot coflow (JHC) burner with 3 and 9% oxygen mass fraction in the oxidizer stream is numerically simulated. A comparison of different turbulence models and kinetic mechanisms is reported based on the Eddy Dissipation Concept (EDC) combustion model. Turbulence was modeled using four variants of the k–ε model including the standard, modified, realizable and RNG together with the Reynolds stress model (RSM). Three different chemical reaction mechanisms including the KEE, DRM–19 and DRM–22 are also compared. Comparison of temperature and mixture fraction profiles between the experimental and predicted values illustrated that for the unconfined, axisymmetric JHC flames reasonable predictions can be obtained employing the modified k–ε model together with KEE chemical kinetic mechanism. For the 3% flame, however, some improvements on the predicted peak flame temperature were achieved using the DRM–19 with more computational cost.<\div>

۳CFD Based Simulation of Binary Droplet Coalescence
نویسنده(ها): ، ،
اطلاعات انتشار: سومین کنفرانس ملی کاربرد CFD در صنایع شیمیایی، سال
تعداد صفحات: ۱۱
Computational Fluid Dynamics (CFD) technique has been used to simulate the coalescence of binary water droplets. The Volume of Fluid (VOF) approach has been applied for interface tracking. In addition a parametric study has been carried out to investigate the coalescence time as a function of some parameters consisting of the collision velocity, oil viscosity, interfacial tension and off–center collision. The simulation results were validated by comparing with published experimental data. The results revealed that coalescence would be faster with higher collision velocity. Moreover, the larger interfacial tensions and less oil viscosity decrease the coalescence time. Dimensional analysis was used to concentrate the results in the form of a predicting correlation for coalescence time.<\div>

۴Experimental Study and 3D CFD Simulation of Different Catalyst Loading Effects on Trickle Bed Reactors Hydrodynamics
نویسنده(ها): ، ،
اطلاعات انتشار: سومین کنفرانس ملی کاربرد CFD در صنایع شیمیایی، سال
تعداد صفحات: ۱۲
Single–phase pressure drop has been studied in a range of flow rates that is of particular interest to trickle bed reactors. Bed is packed with industrial trilobe and cylindrical catalysts with 1mm diameter and 4.2 mm length and 1.6 mm diameter and 3.7 mm length respectively. Particles were packed random close or dense packing (RCP) and random loose packing (RLP). The Bed bulk porosities have been obtained 0.43 and 0.47 for RCP and RLP for trilobe and 0.44 and 0.48 for cylindrical respectively. In this study a CFD model based on Eulerian–Eulerian approach has been developed and User Define Functions are prepared for accurately predict the inter phase momentum exchange and radial porosity distribution on reactor. The two fluid model which developed by Attou & Ferschneider has been used for inter phase momentum exchange in momentum balance equation. An experimental set up is also providing for validation of CFD results. The CFD results had very good agreement with experimental data of this work for trickle bed reactor. Also it is shown that the pressure drop of dense loading is bigger than loose packing. It is found that the trilobe catalyst has generally higher pressure drop than cylindrical catalyst because of more tortuosity.<\div>

۵CRITICAL STATE BEHAVIOR OF AN UNSATURATED SILTY SAND
نویسنده(ها): ،
اطلاعات انتشار: ششمین کنفرانس بین المللی زلزله شناسی و مهندسی زلزله، سال
تعداد صفحات: ۸
Critical state models for unsaturated soils have been proposed in recent years however the proposed models have been based on limited experimental data. In this paper a laboratory study for verifying influence of matric suction on the shear strength and mechanical behavior of a silty sand is presented . for thiw purpose a set of triaxial tests in saturated and unsaturated conditions have been carried out with the aim of considering the sucion effect and its chanes during fast rate of loading such as earthquake.<\div>

۶AN EXPERIMENTAL STUDY CONCERNING THE EFFECTS OF NON PLASTIC FINE AND PHYSICAL PARAMETERS ON THE LIQUEFACTION RESISTANCE
نویسنده(ها): ، ، ،
اطلاعات انتشار: ششمین کنفرانس بین المللی زلزله شناسی و مهندسی زلزله، سال
تعداد صفحات: ۸
For sand mixed with non–plastic fine, the void ratio related to sand grains ( ) plays a more important role in comparison with the total void ratio, where soil liquefaction resistance will be improved due to increase in FC at the constant . In spite of this fact, the recent works indicate that is unable to show perfectly the role of the non–plastic fines that are in voids between sand grains. For this reason, an equivalent void ratio has been defined that takes into account the non–plastic fine participation ratio in the soil bearing skeleton. In the present work, the generality of the expression of is verified. For this, a set of static undrained triaxial tests were performed. The results of tests indicate that, the undrained behavior of a given sand mixed with different percentages of non–plastic fine can be described by . But if the grading curves of sand change, we can not find a logic retention between and undrained resistance of soil, unless the physical and mechanical characteristics of soil are well introduced in expression of .<\div>

۷improvement on Q.Xie threshold proxy signature scheme against collusion attack
نویسنده(ها): ، ، ،
اطلاعات انتشار: نوزدهمین کنفرانس مهندسی برق ایران، سال
تعداد صفحات: ۵
In a t,n threshold proxy signature scheme the original signer can delegate the signing power \to n proxy singners such that any t or more out of n proxy singners can sign messages on behalf of the original signer but t –1 or less of the proxy signers cannot generate a proxy signature in this paper we will improve the security of xie's threshold proxy signature scheme against the new types of collusion attack was presented by liu and tan in 2007 we also present that our improved scheme is more efficient than xie's scheme in terms of computational complexities.<\div>

۸Linear Approximate Model Identification and adaptive Control of Variable Speed Wind Turbine Using Recurrent Neural Network
نویسنده(ها): ، ،
اطلاعات انتشار: نخستین کنفرانس انرژی بادی ایران، سال
تعداد صفحات: ۱۰
The best configuration for generating electricity energy form a variable–speed wind energy conversion system (WECS) is using double–output induction generator (DOIG).Controlling this system in order to optimum performance on maximum extracting power from wind in each speed were attracted theattention of many researchers. This kind of generators use a rectifier and inverter know as static Kramer drive (SKD) and changes on thefiring angle of the inverter can control the operation of the generator. Achieving above purpose is difficult because the behavior of this system under classic controller is very timevariant and nonlinear and need to an adaptive controller is proposed. With regard to high capability of neural network in control subject,in this paper one structure of this kind of networks for controlling wind energy conversion system was proposed. Thiscontroller uses recurrent neural network basedon approximation of non–linear autoregressive moving average (NARMA) model. Feasibility and effectiveness of controller are demonstrated by simulation results. Different cases, such asapplying a distinct disturbance, applying noise to system and Parameters variations anduncertainties of the system in order to study the ability of proposed controllers, were considered<\div>

۹Effects of cement and lime treatment on geotechnical properties of a low plasticity clay
نویسنده(ها): ، ،
اطلاعات انتشار: کنفرانس بین المللی عمران، معماری و توسعه پایدار شهری، سال
تعداد صفحات: ۱۴
In the current study, the effects of two types of additive for the soil (i.e. lime\cement) on the geotechnical and engineering properties of a soil are studied. The results of the study indicate that optimum moisture content, maximum dry unit weight and plasticity index are affected by the addition of cement or lime. Also cement treatment result in increase of unconfined compressive strength (UCS) of the soils significantly. Whereas the test results indicate that there is an optimum of lime content so that the addition of a few percentage of lime results in increase of unconfined compressive strength. Generally, improvement in mechanical behaviours of the soil due to cement treatment was noticeably higher than lime treatment. Also the results of tests show that the change of UCS of the specimens with the initial water content and curing time is significant, so that decreasing of initial water content or increasing of curing time results in increase of USC of the specimens. Also, the current study sought to characterize the relationship between secant modulus (E50) and UCS, curing time and cement or lime content.<\div>

۱۰Reduction of Carbon dioxide Emission through a Novel Configuration of Methanol Synthesis Reactor
نویسنده(ها): ، ، ،
اطلاعات انتشار: هفتمین کنگره ملی مهندسی شیمی، سال
تعداد صفحات: ۱۰
Greenhouse gases (GHGs) warm the surface and the atmosphere with significant implications for rainfall, retreat of glaciers and sea ice, sea level, among other factors. Increased atmospheric CO2 concentration is widely being considered as the main driving factor that causes the phenomenon ofglobal warming. The chemical reduction of carbon dioxide is regarded as the most effective method to reduce carbon dioxide concentration in the atmosphere. A steady–state heterogeneous model for this methanol synthesis reactor was developed. This model is used to compare theremoval of CO2 in this reactor with a membrane dual type methanol reactor (MDMR) and conventional dual–type methanol synthesis reactor (CDMR). A cascade membrane methanolsynthesis reactor is a vertical shell and tube heat exchanger in which the first reactor is cooled withcooling water and the second one is cooled with synthesis gas. The wall of the tubes in the both reactor is covered with a palladium–silver membrane, which is only permeable to hydrogen. The simulation results represent 4.96% and 2.66% enhancement in the CO2 removal rate due to have a favorable profile of temperature along the CMMR relative to CDMR and MDMR, respectively.<\div>

۱۱Simulation of a Novel Combination of Fixed bed and Slurry Bubble Column Reactor Concept for Methanol Synthesis
نویسنده(ها): ، ، ،
اطلاعات انتشار: هفتمین کنگره ملی مهندسی شیمی، سال
تعداد صفحات: ۱۱
In this work, a novel combination of fixed bed reactor and slurry bubble column reactors for methanol synthesis has been proposed. In the first catalyst bed (Fixed bed reactor), the synthesis gas is partially converted to methanol in a water–cooled reactor. In the second rector (Slurrybubble column reactor) which is a gas–cooled reactor, the reaction heat is used to preheat the feed gas to the first bed. in this work, Carbon monoxide injection to second reactor (slurry bubblecolumn reactor) was considered. On the other hand proficiency of two types of industrial dual typemethanol reactor (IDMR) and fluidized–bed membrane dual–type methanol reactor (FBMDMR) are used as a basis for comparison in terms of methanol production, CO and H2 conversions in the same condition. Simulation results show 13.3% and 7.92% enhancement in the yield of methanolproduction in comparison with IDMR and FBMDMR respectively while 10% CO was injected to the slurry bubble column reactor.<\div>

۱۲Prediction of Droplet size in a Rectangular Venturi Scrubber based on Eulerian\Lagrangian Method
نویسنده(ها): ،
اطلاعات انتشار: هفتمین کنگره ملی مهندسی شیمی، سال
تعداد صفحات: ۸
Venturi scrubbers are extensively utilized in gas cleaning. The cleansing elements in these scrubbers are droplets formed from the atomization of a liquid into a dust–laden gas. In this study,a mathematical model based on Eulerian\Lagrangian method has been developed. This model considered Eulerian approach for gas stream motion and Lagrangian approach for droplet movement. Moreover, In order to model the evolution of the polydisperse droplet phase, thepopulation balance equation (PBE) is coupled to the continuity and momentum balance equations. The velocity field of gas flow was determined using k–) turbulence model. The results from the model are in good agreement with the experimental data. After validating the model the effect ofoperating parameters such as gas velocity and distance from liquid injection point was used to predict mean diameter of droplet. It was found that all these variables significantly affect to droplet size<\div>

۱۳Large eddy simulation of a tree–stream jet–in–hot–coflow flame
نویسنده(ها): ، ،
اطلاعات انتشار: هفتمین کنگره ملی مهندسی شیمی، سال
تعداد صفحات: ۱۰
Large Eddy Simulation (LES) with finite–rate\eddy dissipation combustion model is applied to simulate transient behavior of a three–stream jet–in–hot–coflow (JHC) flame. Two static SGS models including the Smagorinsky and WALE together with two dynamic SGS models comprising the dynamic Smagorinsky and dynamic kinetic energy have been investigated to resolve sub–grid scale stresses. It is shown that the dynamic SGS models, generally, gives improved accuracy over the static models. In particular, the dynamic procedure of assigning model parameters and non–equilibrium turbulence assumption in the dynamic kinetic energy model are the key factors leading to produce acceptable results for mean and fluctuating temperature fields<\div>

۱۴Investigation of flow Maldistribution in Trickle Bed Reactors Dense and Sock Loading Beds
نویسنده(ها): ، ،
اطلاعات انتشار: هفتمین کنگره ملی مهندسی شیمی، سال
تعداد صفحات: ۱۱
Liquid mal–distribution in catalytic Trickle bed reactor have investigated using porous alumina extrudate trilobe catalysts. Two different catalyst loading methos (dense and sock) were used toevaluate the performances of the dense and sock loaded bed in terms of liquid spreading. Theexperimental setup has capability for studying the effect of bed height on distribution of the liquid for different gas and liquid flow rates. A collector device with seven compartments has been usedin bottom of the reactor to investigate the liquid radial distribution. Furthermore, an Artificial Neural Network (ANN) algorithm has been applied to predict the effective parameters on liquid spreading in trickle bed using the obtained experimental data. was concluded that with same liquiddistributor and operating conditions, the sock packed beds distribute liquid better than dense ones.It was explaind that these results are due to the Isotropic distribution of porosity in sock loaded beds in comparison with dense beds. It was observed that any increase in gas and liquid flow rate enhances the liquid flow distribution; however, the effect of liquid flow rate is more considerable.<\div>

۱۵Enhancement of Methanol Production by Sorption–Enhanced Process in a Novel fluidized bed Configuration
اطلاعات انتشار: اولین کنفرانس دوسالانه نفت، گاز و پتروشیمی خلیج فارس، سال
تعداد صفحات: ۶
In the present study, a mathematical model of the fluidized bed reactor for methanol synthesis with in–situ water adsorption is investigated, theoretically. The two–phase theory of bubbling regime is applied to model the fluidization concept. The density difference between binary adsorbent and catalyst particles separate them. The heavy catalyst particles tend to sink and the light adsorbent particles tend to rise. During the methanol synthesis process, the motivation for in situ water removal by using adsorbent particles (Zeolite 4A) is to displace the water–gas shift equilibrium to boost methanol productivity. The simulation results reveal that selective water adsorption from methanol synthesis in Sorption Enhanced Fluidized bed Reactor (SE–FMR) leads to a huge enhancement of methanol production compared to the other configurations.<\div>

۱۶Effects of aflatoxin B1 on growth performance, health indices, phagocytic activity and histopathological alteration in Fenneropenaeus indicus
اطلاعات انتشار: IRANIAN JOURNAL OF FISHERIES SCIENCES، دوازدهم،شماره۴، oct ۲۰۱۳، سال
تعداد صفحات: ۱۴
Mycotoxins contamination of feedstuff for aquatic animals is common in regions with humid tropical conditions. In this study Indian white shrimp, Fenneropenaeus indicus, (11.79 ± 1.76 g) were fed with diets containing 0, 20, 50, 100, 200, 400, 800 and 1600 ppb levels of aflatoxin B1 (AFLB1) for 8 weeks. Final weight, aflatoxin B1 residue (2–week intervals), Total Hemocyte Count (THC), Total Plasma Protein (TPP), Phagocytic Activity (PA), Survival rate (4–week intervals) were determined. Histopathological alterations in hepatopancreas, midgut and muscle tissues were studied at the end of 4 and 8 weeks. Shrimps fed with the 1600, 800 and 400 ppb concentrations of AFLB1 exhibited slow growth, and more reddish discoloration disseminated over the body at 4th week. Growth parameters, survival rate and health indices (THC, TPP) of F. indicus, are affected by the different doses of AFLB1 in diets. At the end of 8th week, doses of AFLB1 in the diets showed negative correlation to final weight, survival rate, THC and TPP (r = – 0.312, –0.603, –0.237 and – 0.649 at P0.001, respectively). Moreover, significant histopathological alterations in the hepatopancreas, midgut and muscle tissues of exposed shrimps to different levels of AFLB1 were observed and these alterations are obviously indicated by changes in the health indexes (THC and TPP).
نمایش نتایج ۱ تا ۱۶ از میان ۱۶ نتیجه