Sharif Digital Repository

In this research, we focus on reduction of solutes in left out water from reverse osmosis membranous units (brine) with reduction of scaling factors of membrane. This research is important from that perspective that the out put brine from reverse osmosis membranous unit After purification by this method, enter into membranous system in order to increase in recovered water volume and also minimization of out put waste from membranous system and decrease the environmental damages. The method used in this research, is three processes of cooling, chemical desalination and seeding by crystal material. In this research is investigated the type and amount of matter for chemical desalination and... 

In this study, a tree-dimensional random pore-scale network model is used to simulate the membrane contactor porous medium. Drainage and imbibition phenomena is simulated to have a better knowledge of liquid and/gas intrusion trough the membrane porous structure. A genetic algorithm is used as an optimization tool. Several variables such as the number, radius and location of pores, the coordination number, as well as the radius and length of the throats are used herein as the optimization parameters. The difference between the binary SEM images and virtual sections on the generated network in conjunction with the permeability and mean pore size data were selected as the objective function.... 

Polysulfone (PSU) and polyethersulfone (PES) porous membranes; and mixed polymers (PSU and PES) with nanoparticles TiO2, were prepared for air humidification. The mechanical properties and morphology of these membranes were studied by Tensile Tester and SEM/EDX. The effects of membrane composition and operating factors on humidifier performance were investigated. The results revealed that the membrane composition and its structure have significant effect on humidification. The porous membranes with finger type cavities had higher humidification performance but lower mechanical properties. The Membranes which were prepared from polysulfone polymer, 10 wt % of polymers in casting solution and... 

Recently separation technology has been developed and engineers are trying to find more rapid and more economic ways in order to reach pure materials. One of the most important needs of human being is natural gas which has some impurities. Acid gases such as carbon dioxide and hydrogen sulfide must be separated from methane. This operation is called gas sweetening. Membrane contactors are equipments recently developed and may be used instead of packed towers for gas sweetening in the future. In this project we designed and made a membrane contacting unit to separate carbon dioxide and hydrogen sulfide from methane. This unit lets you to study the effect of many parameters such as gas and... 

A new technique for surface modification of flat sheet hemodialysis membranes has been investigated. This new strategy presents a dynamic surface modification for membranes in order to assess the hydrophilicity, antifouling, and biocompatibility effects of two functional monomers on dialysis membrane. PSF membranes containing polyvinylpyrrolidone were prepared via phase inversion technique. Afterward, free radical polymerization combined with surface polymerization used to introduce acrylic acid and 2-hydroxyethyl methacrylate onto polysulfone membrane surface. Various monomer concentrations were selected to obtain an optimum condition. Field emission scanning electron microscope (FE-SEM),... 

Treatment of landfill leachate with membrane bioreactor (MBR) in lab and pilot scale have been studied in this research. MBR biological adaptation procedure at start of biological treatment, choose of membrane materials, membrane production with highest treatment performance and lowest membrane foaling have been studied. Mixed liquor suspended solid of MBR at the start of adaptation period was 3000 ppm and at the end of this period became 7000 ppm, microbial community has been changed in this period. Number of microbial species were reduced and number of these adapted species were increased. Five membranes were prepared with different concentration of PVDF polymer, solvent and non-solvent to... 

When oil spill take place, it should be removed rapidly. For control of oil pollution, polymeric foams that absorb oil highly, can be used. These foams are polyurethane and polypropylene that float on water and absorb several times their own weight of crude oil. When a thin layer of crude oil remained on water, it couldn’t be separated by chemical and physical methods. In this cases biological methods will be best and suitable. Therefore absorption and biodegradation of oil spill are executed by immobilization of suitable microorganism on polyurethane foam. But current polyurethane foams aren’t biodegradable so this incompetence should be solved. Polyurethane foams compose of two basic... 

In this study, membrane distillation process was used for treatment of high salinity waters. The focus of this study is to simulate and build a setup of membrane distillation process. Since the membrane distillation process is based on the driving force of the temperature difference, the required temperature is provided by both the use of heaters and the use of solar energy. To increase the feed temperature by solar energy, a black polymer coating on the main membrane is used. The main membrane used in this process is PVDF polymer and the polymer coated on the surface is the PAN polymer. After simulating and constructing the laboratory setup, the influence of a variety of parameters on the... 

Since the Iranian oil terminals company(I.O.T.C.) has been the main and strategic gateway of exporting petroleum in the country and plays an important role in the optimum continuity of national, regional and international energy supply chain and also conducting the needed projects whit a desirable quality and minimum time and cost has a prominent influence on steady continuity of manufacturing, importing and exporting of petroleum and gas production. The main purpose of doing this thesis is diagnosing the process of approval, design and implementation of projects in the I.O.T.C., Thus, whit regarding to the modern needs of implementing projects and the necessity of reviewing the structure... 

In this research, droplet motion in symmetric and asymmetric junctions in micro and nano scales was investigated. Droplets motion in symmetric and asymmetric junctions have many applications in many industries such as chemical and pharmacy. In this research symmetric T-junction in micro and nano sizes was simulated numerically in 2D and 3D formes. Also asymmetric T-junction (with unequal width branches) was simulated numerically in two cases, 2D and 3D. In the asymmetric T-junction, also an analyrical theory was developed. Numerical simulation was performed by using VOF techniqe and analytical theory was developed by thin film theory. For verifying the accuracy of numerical solution, grid... 

We studied dynamics of droplets inside channels under surface forces created by chemicalsteps on the channel walls. A multi-component Shan-Chen lattice Boltzmann method isused for this purpose.The effects of parameters such as the channel height, viscosity anddensity ratios on the results were investigated for homogeneous and grooved substrates. Alsoan analytical solution was developed for droplets under chemical heterogeneities in channels with smooth surfaces. The solution considers a general condition, namely, asymmetry of the contact angles on the top and bottom walls, the viscosity of the gas as the second fluid and the effect of the channel height. Then using Shan-Chen lattice... 

Hydrodynamic mesoscopic equations are solved using boundary integral method to investigate the coarsening dynamics of two dimensional nanodroplets. The dynamics is probed by locating two drops on homogeneous, chemical heterogeneous and physical heterogeneous substrates respectively. For homogeneous substrate, the effect of different parameters like droplets distance, slip boundary condition, surface contact angle and disjoining pressure type on the dynamics is studied. Results reveal that increasing the contact angles to values larger than a critical value may qualitatively change the coarsening process and the profile of the disjoining pressure can appreciably modify the coarsening rate.... 

A droplet placed on the boundary of two solids with different wettabilities will move to the more wettable part. This is a well-known phenomenon and has been extensively used in a variety of processes and applications ranging from biological systems and ink jet printing to the commercial lab-on-a-chip. Because of its importance, many studies are conducted around this phenomenon. The difference between the equilibrium contact angles of the droplet on the two parts gives rise to an interfacial driving force which moves the droplet. Such a motion is not continuous as the droplet slides to the more wettable area, the driving force diminishes and consequently the droplet stops. A non-stop motion... 

Mesoscopic hydrodynamic equations are solved employing a VOF based method to investigate the equilibrium shape of nanodroplets positioned over various topographic geometries of the supporting substrate for three-dimensional systems. By taking into account liquid-liquid and liquid-solid interactions a complex distribution for inter-molecular forces over the substrates (the disjoining pressure) is observed. In this research we show that motion of nanodroplets not only caused by contact angle difference in drplets two sides, but also depend on disjoining pressure parameters.Geometries with increasing complexities, from wedges to three dimensional edges and wedges, were explored with the main... 

This research concerns investigating the behavior of two-phase flow in the inlet and outlet of the microchannels.Both the droplet based and the continuous microfluidics are considered. For the continuous system whenthe minor fluid enters the microchannel, due to ratio of viscosity of two fluids, viscous folding occurs.Viscous folding phenomena is similar to the buckling phenomena in solids.This means that the viscosity of the fluid, which is applied to two sides of the fluid layer, causes folding the fluid layer and changing the shape of it. For the study we employ a VOF based numerical routine. In order to verify numerical results, the grid and the time step independenciesare checked. In... 

Carbon Nanotube webs exhibit interesting properties when used as thermo-acoustic projectors. This work studies thermo-acoustic phenomena of these sound sources both in near and far field regions. Our three-dimensional simulation and experimental data show pressure waves are highly affected by dimensions of sound sources in near field due to interference effects. Although pressure amplitude increases with increasing frequencies, maximum pressure amplitude reached in lower frequencies may become larger than its maximum amount at higher frequencies because of interference effects. Measurement of different surface area sources shows generation of sound waves in far field is independent of... 

Drag reduction on surfaces always has been a great case of study, especially in transport industry. This project discusses the external laminar flow of a single-phase fluid over a flat plate and the effects of making rectangular tiny grooves - in micron or millimeter - on them to reduce total drag. Making grooves with appropriate geometry on surfaces causes the fluid-solid contact area on the groove's surface turn into fluid-fluid and as a result the fluid will not shed into the groove. In other words the flow instead of having a no-slip boundary condition on inner surfaces of the groove, creates vortices in them that causes a remarkable reduction in velocity gradient followed by a skin... 

This project studies the effects of different blade and different velocity fields on reducing drag coefficient. A numerical simulation was set up for a circular cylinder to represent the effects of blade on reducing drag. In this study, velocity, density and the cylinder diameter were constant and different viscosities were selected for different regime flows. The computational fluid dynamic programmer FLUENT was used to simulate results for this project. Arrays of cylinders were set up to see the changes in velocity profiles and drag coefficients for a range of Re. In this study, I studied three cases of setting up blade and concentrated on friction drag coefficient and pressure drag... 

Carbon nanotubes have special thermodynamic properties which makes suitable as a thermo-acoustic sound source. Recently it is shown that by using these nanotubes it is possible to generate strog sound waves in air or water. Experimental analysis of phenomenon can be complicated and expensive. Hence this fact, in this study using molecular dynamic simulation, numerical analysis of sound generation with CNTs in air and water is discussed. For this purpose, the required structue of the system is generated and it has reaced equilibrium. This process has been done for 6 different CNT and for each CNT there are 5 different distances between them. Althogether, 30 different cases has is used for...