Sharif Digital Repository

In situ mixing by dispersive transport of salt and viscous fingering between the injected low-salinity (LS) brine and high-salinity (HS) formation brine can jeopardize the performance of low-salinity waterflooding (LSWF). In our previous papers, we demonstrated that in situ mixing can be suppressed by polymer-enhanced low-salinity waterflooding (PELS), in which a small amount of a viscosifying agent, such as a polymer, is added to the LS stream. Nevertheless, effective mixing control with PELS depends upon several factors and operational conditions, which have not yet been addressed. Therefore, this research focuses on the investigation of the impact of injection parameters, such as the... 

This paper proposes a model-based design approach for microgrids considering the aging of power electronic devices under different operating conditions. The proposed approach takes into account the physics of failure mechanisms in converter components as the failure prone devices in power systems. Furthermore, it considers the impacts of load profile on the aging of converter components and system performance. This approach facilitates accurate and optimized design of power electronic-based microgrids. According to this approach fragile links of power converters for a specified application can be identified. Moreover, the weakest converters based on their function in the microgrid can be... 

The concerns regarding the consumption of traditional fuels such as oil and coal have driven the proposals for several cleaner alternatives in recent years. Hydrogen energy is one of the most attractive alternatives for the currently used fossil fuels with several superiorities, such as zero-emission and high energy content. Hydrogen has numerous advantages compared to conventional fuels and, as such, has been employed in gas turbines (GTs) in recent years. The main benefit of using hydrogen in power generation with the GT is the considerably lower emission of greenhouse gases. The performance of the GTs using hydrogen as a fuel is influenced by several factors, including the performance of... 

A series of wind-tunnel tests were conducted on a Y-shaped diverterless supersonic inlet (DSI) in order to investigate its performance at various operating conditions. The present DSI was designed for a freestream Mach number of M∞ 1.65. The experiments were performed at supercritical, critical, and subcritical operating conditions and at 0 deg angle of attack and angle of side slip. The results showed that the present DSI had an acceptable performance at its design condition. A symmetric supersonic flow pattern was observed at both supercritical and critical operating conditions. At low subcritical operating conditions, the supersonic flow pattern remained symmetric too. However, at high... 

The paper presents a comparison of steam methane reforming (SMR), sorption enhanced steam methane reforming (SE-SMR), auto-thermal reforming (ATR), and sorption enhanced auto-thermal reforming (SE-ATR) in a fixed bed reformer for hydrogen production. A one-dimensional, unsteady-state heterogeneous reactor model for each process which includes mass and thermal dispersion in the direction of flow and axial pressure distribution, has been simulated using gPROMS® 4.0.1 model builder, while CEA and Aspen Plus® have been employed to analyze the equilibrium performance and simulate the process flowsheets of individual process respectively. The performance of the individual hydrogen production... 

Increasing the integration of distributed energy resources (DERs) inspired by environmental and governmental incentives, beside the introduction of multi-agent structure perspective have led to a paradigm shift of operational conditions in distribution systems. In this context, the traditional concept of fit and forget in the distribution grid management would not be efficient in the modern distribution systems and consequently new mechanisms should be developed in order to enable the distribution system operator (DSO) to efficiently manage the grid congestion caused by peak power output of DERs or load demands requests. In this article, the Stackelberg game concept is employed to develop an... 

This paper presents a hierarchically distributed algorithm for the execution of distribution state estimation function in active networks equipped with some phasor measurement units. The proposed algorithm employs voltage-based state estimation in rectangular form and is well-designed for large-scale active distribution networks. For this purpose, as the first step, the distribution network is supposed to be divided into some overlapped zones and local state estimations are executed in parallel for extracting operating states of these zones. Then, using coordinators in the feeders and the substation, the estimated local voltage profiles of all zones are coordinated with the local state... 

The solar collectors absorb solar irradiation and then produce thermal energy; however, they cannot generate electrical power. Electricity and thermal energy can be produced by the photovoltaic thermal module, simultaneously, while the outlet temperature of the photovoltaic thermal module is not usually high enough to provide thermal requirements of a building such as hot water or space heating. This work proposes a novel compound system created by the connection of a solar collector in series with a photovoltaic thermal module to resolve the issue of low outlet temperature in the photovoltaic thermal module and lack of electrical power in solar collectors. To examine the feasibility of this... 

Potent carbon-neutral energy carriers bring a vital solution for sustained industrialization and environmental protection. Hydrogen as a novel zero-emission energy carrier offers more than twice energy per unit mass compared to other fuels. Membrane reactor technology transforms gray hydrogen to blue by selective hydrogen separation and carbon dioxide capture from the product mixture. Moreover, improved reactant conversion during reversible steam reforming of methane, methanol, and ethanol; water gas-shift; and dehydrogenation of cyclic and aliphatic hydrocarbons as well as enhanced hydrogen yield are results of selective and distributed hydrogen separation from membrane reactor. In this... 

Kinetic data relevant to steam methane reforming (SMR) are often applied to catalysts and conditions for which they have not been derived. In this work, kinetic rates for the two SMR and water gas shift reactions were derived for 12 commonly used reforming catalysts based on conversion data obtained from the literature. Subsequently, these rates were tested in dynamic operation, steady-state, and equilibrium using a 1-D reactor model developed in-house with gPROMS model builder. Modelling outputs were further validated independently at equilibrium using the software chemical equilibrium with applications (CEA), and the literature. The effect of variables such as temperature, pressure, steam... 

This paper introduces a new methodology for designing and optimizing the performance of hydraulic Cross-Flow turbines for a wide range of operating conditions. The methodology is based on a one-step approach for the system-level design phase and a three-step, successive numerical analysis approach for the detail design phase. Compared to current design methodologies, not only does this approach break down the process into well-defined steps and simplify it, but it also has the advantage that once numerical simulations are conducted for a single turbine, most of the results can be used for an entire class of Cross-Flow turbines. In this paper, after a discussion of the research background, we... 

The safe operating condition for the vacuum tubes is very important and critical since they are very expensive and delicate. Providing limited short circuit energy for the vacuum tube and fast transferring from the short circuit to the nominal operation state are absolutely necessary. Extant protection strategies threat the availability of the vacuum tubes. In addition, they cannot completely protect the tube due to the delay of the fault detection system. This article proposes a high voltage (HV) short circuit fault current limiter which can limit the short circuit energy of the system inherently. The proposed structure activates automatically when the current exceeds the predetermined... 

Clamp mode resistor capacitor diode (CMRCD) snubbers have a simple and easy implementing structure. They have been widely adopted in the pulsed power supplies to provide a safe operating condition for the series insulated gate bipolar transistors (IGBTs). The main problem of the CMRCD snubbers is their poor performance in the voltage balancing of the series IGBTs. They are essentially overvoltage protectors and clamp the voltage of the IGBTs in a probable potentially dangerous condition. This issue diminishes the expected lifetime of the series IGBTs, where a number of them face a higher level of the voltage than that of the others. The unbalanced voltage of the series IGBTs will result in a... 

The self-supported CuxNi0.6-xMn0.4Fe2O4 oxygen carrier (x = 0.1–0.5) is synthesized to be applied in the chemical looping steam methane reforming (CL-SMR) process through the synthesized co-precipitation method. The response surface methodology (RSM) based on the Box–Behnken model is adopted to evaluate the effects of independent variables on the functionality of responses as well as predicting the best response volume. In this method, the variables consisting of reaction temperature (550–700°C), oxygen carrier (OC) loading percentage (0.1–0.5), steam-to-CH4 ratio (S/C), (1.5–3.5), and redox cycles’ count (10–24) and the responses consisting of hydrogen (H2) production yield, CH4 conversion... 

In this paper, the performance of the sparse reconstruction (SR) and the delay-and-sun (DAS) methods for damage localization, were evaluated for various environmental and operational conditions, both numerically and experimentally. To assess these damage localization methods, a methodology based on the Taguchi method was used to make the experimental design, and a modified performance-index was defined to represent the quality of reconstructed images. Then, the robustness and the accuracy of each method, in a well-defined performance region relevant to in-service aerospace structures, were investigated using the Taguchi and analysis of variance methods. It was concluded that for the defined... 

Optimization of the placement and operational conditions of oil wells plays an important role in the development of the oilfields. Several automatic optimization algorithms have been used by different authors in recent years. However, different optimizers give different results depending on the nature of the problem. In the current study, a comparison between the genetic algorithm and particle swarm optimization algorithms was made to optimize the operational conditions of the injection and production wells and also to optimize the location of the injection wells in a southern Iranian oilfield. The current study was carried out with the principal purpose of evaluating and comparing the... 

Advanced accident tolerant cladding materials have brought up the potential to delay the deleterious consequences of loos of coolant accidents related to slowing down hydrogen formation from reaction of zirconium with steam in order to minimize the additional heat generation and improve fuel and cladding retention of fission products. The performance improvement offered by these advanced materials may expand the operating envelope of existing light water reactors. This paper examines the neutronic performance of the VVER-1000 light water reactor for the application of accident tolerant cladding in order to realize the endurance of severe accident conditions. This study includes a detailed... 

Organic Rankine Cycles (ORCs) are promising approaches for generating power from medium or low temperature heat sources. In this regard, ORCs can be used to indirectly produce power from solar energy. Due to intermittent nature of solar energy, storage unit should be coupled with solar ORCs to improve the output power and operating hours. In this article, studies on solar ORCs integrated with various types of storage units were reviewed; the main findings of such studies were extracted and provided. Based on the findings, several factors such as the temperature and pressure at the inlet of the turbine, as well as the operating condition affect the performance of solar ORCs with thermal... 

In this study, the performance of a system consisting of an organic Rankine cycle (ORC) for generating power and an electrolyzer for producing hydrogen with a zeotropic mixture as working fluid to recover waste heat in a geothermal flash-binary cycle is investigated from energy and exergy point of view. The study also investigates the effect of using zeotropic mixtures with different compositions as the ORC's working fluid rather than pure fluids. Using the particle swarm optimization (PSO) algorithm, the optimization is performed to maximize the power production of the entire system. The results show that using the combination of pentane with other pure fluids as working fluid led to... 

A new nanocomposite polymer gel is synthesized for reduction of excess water production in petroleum reservoirs at real operating conditions. This new nanocomposite gel contains SiO2 nanoparticles, partially hydrolyzed polyacrylamide (HPAM) and chromium triacetate. High pressure and high temperature tests using porous carbonate core are carried out to evaluate the effects of nanoparticles on the synthesized polymer gel performance. It is shown that the residual resistance factor ratio of water to oil using the synthesized polymer gel nanocomposite in this work is much higher than that of the ordinary polymer gels. The presented results confirm the high performance of the synthesized...