Sharif Digital Repository

A gas cyclone is a fixed mechanical device that uses centrifugal force to separate solid particles from gas. Gas containing particles is brought tangentially into the cyclone. This results in the development of a vortex, which applies strong centrifugal forces to the particles. The larger particles move toward the outer wall of the system as a result of centrifugal forces. gases spiral down from a tangential inlet towards the conical section, where the flow is reversed and the particles are collected in a hopper. The gas phase then proceeds upward in an inner vortex towards the gas exit via the vortex finder.
In this study swirling flow of two-phase gas-solid in cyclone separator is... 

This project reports an experimental work on the convection heat transfer of nanofluids, made of -AL2O3 nanoparticles and de-ionized water, flowing through a copper tube in the laminar flow regime. The results showed considerable enhancement of convective heat transfer using the nanofluids. The enhancement was particularly significant in the entrance region, and was much higher than that solely due to the enhancement on thermal conduction. It was also shown that the classical Seider and Tate equation failed to predict the heat transfer behavior of nanofluids. Possible reasons for the enhancement were discussed. Migration of nanoparticles and the resulting disturbance of the boundary layer... 

Forced convection in a parallel plate channel filled by porous medium, with walls held at constant heat flux is investigated. A criterion for employing a local Thermal Equilibrium assumption between solid matrix and fluid in a porous channel is developed. Darcy-Brinkman-Forchheimer momentum equation is solved by Homotopy perturbation method. The energy equation for solid and fluid phases employing Local Thermal Non Equilibrium (LTNE) assumption is solved for fully developed and thermally developing forced convection. The analysis leads to an expression for fluid and solid temperatures and also the local Nusselt number. The effect of pertinent parameters such as the Darcy number, the Inertia... 

The objective of this project is numerical simulation of air flow and heat transfer between two horizontal concentric cylinders with rotation of inner cylinder and inertia of outer cylinder grooves on the inner cylinder. In this study, the air, meanwhile rotational motion by the inner cylinder will enter into the annular space between two cylinders with certain flow rate. It can be mentioned to cooling of power plant generators, Electric motors and rotating machines among usages of air flow between two cylinders. In this article the objective is calculation of pressure drop and Nusselt number, temperature distribution on the inner cylinder under conditions of constant temperature of... 

Fuel cell is a power generator like internal combustion engines, but the first point is that internal combustion engines produce mechanical power while fuel cells produce electrical power. Secondly, internal combustion engines use hydrocarbon derivatives such as gas as fuel and their exhaust fumes are toxic gaseous, but fuel cells use hydrogen as fuel and their exhaust are only water in either vapor or liquid form. One of the most important issues in fuel cells is optimum design of micro channels of bipolar plates which is different regarding the type and application of fuel cells. Optimum designing of micro channels on bipolar plates plays a key role in fluid mass transport through micro... 

In recent years, many advanced Computational Fluid Dynamics (CFD) methods have been developed for accurate and efficient simulation of fluid flow. The application of these methods shows that for sufficient accuracy, the mesh resolution has to be reasonably high. Unfortunately, conventioanal single-grid Navier-Stokes solvers suffer from poor convergence characteristics. For this problem we used Multigrid method to speed up the convergence rate. In this section a code was developed (based on the conventional CFD algorithm) which can solve Navier-Stokes equations on structured grids. It also simulates the free surface by VOF method. Agglomeration multigrid method is used in present study for... 

In this thesis, we study the effect of cognition and cooperation on two important MAC layer performance metrics, i.e. maximum stable throughput and delay. To this end, we consider a broadband secondary user which interferes with N narrowband primary users. In our study we focus on four transmission protocols as well as two transmission policies, i.e. parallel and non-parallel transmissions. In the cooperative protocols, the broadband transmitter relays the packets of the primary users which have not correctly decoded at the primary receiver. In non-parallel transmission case, the packets of the broadband user are transmitted in the total available bandwidth and in parallel transmission case,... 

One of the most important factors of reducing durability of concrete structures is corrosion of steel reinforcement in concrete. In this paper, corrosion behavior of reinforcing steel in concrete is investigated in two different methods of protection based on neural network. As regard the first method, pozzolanic additives with optimized percentage were added to Concrete mix design (the percentage of these additives are 25% Weight of cement of fly ash, Micro silica with 10 percent of weight of cement and 25% of Blast Furnace slag weight of cement). In the second approach of protection, 0/5 percent weight of cement of ferrogard 901 inhibitor is added to basic mix concrete design and the... 

One of the most important issues among defense is the increasing of the defense power using present facilities. Therefore, optimal setting and arrangement of equipment by considering different air-to-earth attack of enemy without knowing of properties and capabilities of available systems may not be possible. So, using defense equipment considering properties of them, and paying attention to existence restrictions and effective elements can have an effective role with the design of suitable algorithm.The main purposes of this thesis are: maximization of the efficiency of a defense system against. aerial invader targets, achieving the best arrangement of defense equipment based on suggested... 

In this dissertation we will study the problem of transmitting the information of continuous source over fading channel, especially when the transmitter does not have complete information about the channel status. In this situation we will have a tradeoff between the Quality of received packets and the Reliability in transmissions. To increase the quality of packets, for example, we should increase the quantization, and therefore, the transmission rates at the transmitter. But this will also increase the Error Probability at the receiver. It means that if the receiver gets the transmitted packet, it will have a better estimation of information source, but it is likely that error happens and... 

One of the most heatedly debated issues in Computer Science is Outlier Detection due to its vast and substantial applications such as credit cards, Image Processing,tax fraud detection, and medical approaches. Consequently, Outlier detection has been researched within various domains and knowledge disciplines. On the other hand, the research attempts have not been sufficient to overcome this critical problem considerably inasmuch as nearly all proposed techniques are associated with a special kind of applications or datasets.Firstly, this thesis attempts to provide a precise definition which not only excludes other one’s drawbacks, but also has its distinctive merits. Three essential... 

Tehran Refinery, as an industrial center that has significant water consumption in Tehran, intends to use the flow of water from the treatment plant south of Tehran after final preparation, with the aim of managing water resources and meeting its needs. And it uses a biological activated carbon (BACF) filter to reduce the DOC concentration. In these filters, the removal of organic matter is performed by the adsorption process as well as the biodegradation process by microorganisms grown on activated carbon. The presence of biofilm leads to continuous bio-regeneration of activated carbon during the water treatment process. Therefore, in this study, by examining the performance of these... 

Code clones are similar code snippets in software projects. Code clones, along with their disadvantages and applications, have long been studied by researchers. In recent years, due to the popularity of open source software, using software development ecosystems such as GitHub have increased dramatically. These ecosystems allow their users to perform high-quality software development without the need for physical presence. A number of previous studies have shown that software is being developed or modified repeatedly and many defects in software projects are duplicates. Finding these recurring codes and defects may be useful for software developers. Given that finding and fixing software... 

In the current era, the urgent need to reduce the use of fossil fuels and limit carbon emissions has highlighted the importance of shifting from traditional gasoline-powered vehicles to electric vehicles. The evolving landscape and challenges in the field of electric vehicles highlight the importance of ensuring the safety and reliability of energy storage systems. Lithium-ion batteries play a central role in electric vehicle technology, requiring thorough research efforts. Notably, the detection of internal short circuit, a common issue in lithium-ion batteries, has become a focus of researchers in recent years. This study aims to investigate the internal short circuit fault in lithium-ion... 

“Progress” is among most frequently used terms in the past few centuries in public discussions, scientific communities as well as economic and sociopolitical policy making. This term has been used in our daily conversations so frequently that it seems to become an intrinsic goal for human beings. However, even a short survey of the introduced meanings of and suggested approaches to achieve “progress” during the last four centuries - since the term was first used- demonstrates that we are faced with a multitude of views from the different - and sometimes contradictory - schools of thoughts. Unfortunately, in recent decades, despite our national desire to “progress”, we have not yet thought...