Sharif Digital Repository

In this study, a new resorcinol-formaldehyde xerogel was synthesized based on sol-gel technology and employed as a sorbent for micro solid phase extraction (µ-SPE) of BTEX and some selected pesticides from aqueous samples.
In the first part, a µ-SPE method in combined with headspace solvent microextraction (HS-SME) along with gas chromatography- mass spectrometry detection (GC–MS) was developed for the analysis of BTEX in aqueous samples. In our knowledge, this is for the first time that these two different extraction methods has been coupled to maximize the advantage of each extraction method. Influential parameters such as the peristaltic pump flow rate, extraction volume, extraction... 

Membranes are one of the best water and wastewater treatment methods that could successfully replace other less-effective conventional techniques such as adsorption, coagulation, etc. Moreover, relative to other techniques, the quality of the water produced by membrane separation is very high compared to others. One of the main drawbacks of membrane treatment is fouling of the surface and internal pores of the membranes restricting its widespread application in the industry.In this study, TiO2@MIL-88A (Fe) photocatalyst and polyacrylonitrile membrane were modified with this photocatalyst to remove humic acid under visible light irradiation inside the PMR photocatalytic reactor was... 

Flow turbulators have crucial importance in heat transfer and energy harvesting applications. Therefore, in this study, the thermo-hydraulic and vibrational behavior of the floe inside a circular tube with vibrational ball turbulators (VBTs) on an axial elastic wire is experimentally studied for the first time. In this novel design, the elastic wire facilitates turbulence by allowing VBTs to move transversally and rotationally and agitate the flow substantially. The effects of diameter and longitudinal distance (pitch) ratios of VBTs, the Reynolds number, and the axial tension of the wire, on the flow friction factor (f), the Nusselt number (Nu), the thermal performance factor (η), in... 

The purpose of this study is investigation of the effect of the porous medium permeability on heat transfer and pressure drop inside tube and compare the results with non-porous tube. In order to create porous medium in this research iron bullets with 2.93, 4.74 and 6.97 (mm) diameters has been used in test tube. Test tube made of copper with an inner diameter of 2 cm and has 1meter length. This experiment is done in steady state, transient and turbulent flow regime (2600< <12260) and also for constant heat flux boundary condition . The experimental results show that the values of heat transfer and pressure drop of porous pipe is always greater than non-porous pipe and these values will... 

Drop formation is an interesting field of research due to its wide-range of applications, such as drug delivery, biomedical studies, pharmaceutical industry, Lab-On-Chip (LOC) devices, etc. In recent years, researchers have used numerical studies to better understand how the process of forming and carefully examining the factors that affect quality improvement. One of the most effective methods in controlling the size and the process of drop formation is use of external force in microfluidic devices. Among the external force in this study, an electric field with oscillating current was used. Rapid methods for creating, deforming, and breaking up of drops in microfluidic applications are... 

Todays, heat recovery steam generator (HRSG) systems are used extensively in combined power plant cycles (consisting of Rankine cycles and Brighton gas cycle) to maximize their efficiencies. The role of HRSG is essential in providing additional energy needed in the steam cycle part. The HRSG has many pipes or harps. They recover the heat from the incoming gas from the gas turbine outlet, which may be boosted up by the duct burner unit. The main challenge in simulating heat recovery units such as tube bundles is to provide ultra-large and cost-efficient grids. In such situations, alternative models are used to simplify the simulation of the steam generator in full scale, including the... 

Nowadays, beside of two-dimensional tungsten disulfide nanosheets, its hybrid nanostructures also provide active sites for physisorption of gas molecules due to their high surface-to-volume ratio, surface active site (such as sulfur vacancies, surface defects, and p-n junctions) and active edges, and are very attractive for gas sensing applications. In this research, tungsten disulfide layered crystallines were grown by chemical vapor phase transport and its two-dimensional nanoflakes were prepared by liquid exfoliation method. So, a thin film of the nanoflakes was deposited on a silicon oxide substrate by drop casting method, and its gas sensing properties were investigated for water and... 

Nowadays adhesives with the development of technology and the numerous benefits they have, are becoming a replacement for traditional joining methods in industries like electronics, automotive, aerospace, and naval. That’s why the need for studying the fracture behavior of adhesive joints becomes vital. So far, many engineers and designers are trying to investigate the behavior of adhesive joints in different conditions that these joints actually deal with. Also, finding solutions to predict the behavior of adhesive joints is the researchers’ other concern. The purpose of this research is to find the effect of factors that are less focused in the literature, on the fracture of adhesive... 

When the fluid passes through the microchannel, some energy is lost due to drag force and pressure drop. One of the methods used in the last few decades to optimize energy consumption is creating superhydrophobic surfaces in microchannels. These surfaces, with their features such as increasing the contact angle and reducing the contact angle hysteresis, can reduce energy loss, which is due to the presence of unevenness on the surface, and by trapping air and creating a two-phase flow, they reduce the drag force. On the other hand, the air trapped inside these irregularities will also affect the heat transfer of the passing fluid in the microchannel, which by creating resistance in the... 

Today, the world is facing the limited resources of fossil fuels and the pollution caused by them. One of the best alternatives that can be offered to fossil fuels is the use of hydrogen in fuel cell technology. Polymer electrolyte membrane fuel cell is one of the types of fuel cell that has a significant advantage over other types of fuel cell in terms of low working temperature and high performance speed. In order to become more widespread, the fuel cell must be freed from the two problems of uncertainty and short life. These two factors can be improved by using a condition monitoring system in both stationary and transportation applications. By using continuous status monitoring and error... 

Energy harvesting from wasted environmental energy to power low-power electronic devices has emerged as an enabling technology for wireless applications in the past decade. The purpose of this technology is to provide remote power sources and/or recharge storage devices such as batteries and capacitors. This concept has environmental implications in reducing chemical waste produced by replacing batteries and potential monetary benefits that also reduce maintenance costs.Energy harvesting (EH) from untapped natural energy sources is common nowadays due to the increasing demand for electricity. Sources have the potential to generate micro to milliwatt power, depending on environmental... 

Considering the importance of oil and gas industries in Iran, issues related to drilling and exploitation of oil and gas fields are among the country's priorities and challenges in industries, research centers and universities, and extensive research is conducted in this field. Since during the process of oil production from oil wells and reservoirs, the formation of multiphase flows, including two-phase fluid flow, is inevitable, investigating the behavior of multiphase fluids, which is a branch of fluid mechanics, is of special importance. In this regard, in continuation of the research conducted in the Faculty of Chemical and Petroleum Engineering of Sharif University of Technology, in... 

Droplet-based microfluidic logic gates have many applications in diagnostic tests and biosciences due to their automation and cascading ability. Although most biological fluids, such as blood, exhibit non-Newtonian properties, all previous studies in this field have been with Newtonian fluids. Additionally, none of the previous work has studied the functional area of logic gates. In the present work, AND-OR logic gate with power-law fluid is considered. The effect of important parameters such as non-Newtonian fluid properties, droplet length, capillary number, and geometrical properties of the microfluidic system on the operating region of the system has been investigated. The results show... 

In this research, numerical simulation of the impact of a drop on a flat surface with oblique velocity has been performed, using two-phase model of Lattice Boltzmann Method (conservative phase-field). During impact, it is important to investigate two-dimensional drop dynamics and to evaluate the effectiveness of the numerical method used. The model used here restores conservative phase field and preserves mass both locally and globally. In addition, to calculate the slope of the phase field, it calls the center points without engaging finite difference calculations. This makes it efficient for running parallel computations. A fixed dry and hard surface is considered and the drop impacts it... 

The increasing growth of marine tourism has strengthened the activities related to this industry. One of the most profitable of these activities is recreational submarines. A traction recreational submarine is an idea in this field, in order to reduce costs, the propulsion force is removed and the submarine is towed by the mother ship. The most important reason for using the traction system and removing the independent drive is to prevent vibration and noise caused by the rotation of the propeller to prevent the escape of aquatic animals and to create a beautiful view from under the sea to watch underwater wonders. Searching for safety and saving people's lives in emergency situations is an... 

Nowadays, the cooling of electronic equipment has become a challenge for designers and scientists due to their progress. One of the most effective solutions for cooling these devices is using microchannel heat sinks. Researchers conducted so many studies experimentally, numerically, or a combination of them to increase the efficiency of microchannel heat sinks. Several methods have been proposed in previous studies to improve the cooling performance, such as using fins, nanoparticles, porous material, etc. Although increasing the heat exchange surface by using fins is caused to increase heat transfer, it also causes an increase in pressure drop. For this reason, researchers are looking for... 

Droplet formation and breakup processes are one of the important steps in many microfluidic devices with a wide range of biological and chemical applications. The purpose of this study is numerical simulation of non-Newtonian droplet formation under the influence of electric field in a microfluidic system. The innovation aspect of this project is the use of non-Newtonian fluid in this process, which, despite many applications in real issues, has been less studied, and in most of the previous researches, Newtonian fluid assumption has been used to simplify the solving. Also, simultaneously, the effects of an external electric field on this process were also studied. Carboxymethyl cellulose... 

Nowadays adhesives with the development of technology and the numerous benefits they have, are becoming a replacement for traditional joining methods in industries like electronics, automotive, aerospace, and naval. That’s why the need for studying the fracture behavior of adhesive joints becomes vital. So far, many engineers and designers are trying to investigate the behavior of adhesive joints in different conditions that these joints actually deal with. Also, finding solutions to predict the behavior of adhesive joints is the researchers’ other concern. The purpose of this research is to find the effect of factors that are less focused in the literature, on the fracture of adhesive... 

Any factor that causes an additional pressure drop to the reservoir is called damage. Damages due to drilling, well completion and production can cause additional pressure drop to formation. In this study, damage caused by mechanical damage, well deviation from vertical (angled well), partially completed well and horizontal well and formation damage behavior during the occurrence of water and gas coning phenomenon have been investigated by simulation and the results have been verified with the analytical models available for calculating the formation skin factor. Also, by studying and examining the data and the results obtained from the simulation of the horizontal well skin factor in a data... 

Various situations of drop impact on solid surfaces occur widely in natural phenomena and industrial applications, as well as involve in the development of some new technologies, such as, 3D printers, interfacial materials, microfluidics, and biotechnology. Therefore, the relevant investigations have been increasing considerably in the last two decades. Most of these studies are related to the simple case of vertical drop impact on horizontal stationary surfaces, while in most cases vertical/oblique drop impact on horizontal/inclined stationary/moving surfaces in the absence/presence of a crossflow and their various combinations occur. One of the most important situations is drop impact on...