Sharif Digital Repository

The gas separation properties of polycarbonate (PC) membranes were investigated in this study. These membranes were prepared via dry and dry-wet phase inversion technique. Pure O2, N2, and CO2 gases were permeated through prepared membranes. The effects of membrane preparation conditions, including solvent type, non-solvent type, non-solvent/solvent volumetric ratio, polymer weight fraction, and drying temperature on the gas separation properties of dry PC membranes were investigated using Taguchi experimental design. Taguchi analysis show that polymer weight fraction offers the most important effect on the separation characteristics of the dry PC membranes. To get the highest... 

The aim of this work was to investigate the performance of different kinds of Linde type A zeolite (LTA) for the dehydration of Tetrahydrofuran (THF)-water solution. Batch experiments were carried out to evaluate the effect of various operating parameters such as contact time, initial concentration, mixing temperature (10, 15,and 25 C), amount of adsorbent, and zeolite type(3A, 4A, and 5A zeolites). In theoretical studies, we took the advantage of several types of equilibrium model isotherms such as Langmuir, Freundlich, Dubin-Kaganer-Radushkevich (DKR) to describe the experimental adsorption data. Besides, three adsorption kinetic models including pseudo-first-order, pseudo-second-order,... 

A power plant cooling tower is like a tower, which needs to be studied very carefully from the aerodynamics point of view. Both the aerodynamics forces on the plume and intake stram are affected by the local winds and the performance of cooling tower decreases. There is a symmetric turbulent flow through the cooling tower if there is no. Wind blowing creates different vorticies, which appear in the lower section of the tower. Their periodic and wuick movments causes deficiency in towers performance and efficiency. Additionally there is wind effect on the plane of cooling tower and this causes a chocked plume which is named Wind Cover. The objective of this study is to decrease the adverse... 

In this study, two units of production of synthesis gas has been stimulated into 2 forms of natural gas complex (steam/Co2¬) reforming and dry reforming. They have been examined from technical and economical views. The product from this process is synthesis gas by the unit ratio of Hydrogen and Carbon Monoxide which is used in Arak petrochemical complex for producing 2EH. For producing this synthesis gas in 900C (reactor temperature) and 15 bar of total pressure , the ratio of feeding parts into reforming reactor for total input carbon (methane and other hydrocarbon) and Carbon dioxide gas and water vapor in representation ( [CH4 + other hydrocarbons : CO2 : H2O ] ) for complex reforming ... 

The dry friction and its effect on the dynamics and vibrations of structures have always been one of the remarkable engineering issues. In the structures of engineering, dry friction mostly exists at the joints of structures and substrates and dry friction can lead to the nonlinearity and even chaos in the vibration of structures. There are different theories for the friction modeling and the most famous theory is the relation between the proportional ratio of the force of friction and perpendicular force to the surface. The main characteristic of friction as a damper force is the change of direction along with change in the direction of velocity. In the present study, at first, the nature... 

Uranium is the most important element in the nuclear fuel cycle. Recovery of uranium from waste produced at every stage of the fuel cycle is not only economically important, but also environmentally important. In the production phase of uranium hexafluoride, certain amount of solid waste is produced in the bottom of the fluorination reactor. In order to extract the uranium from this waste, we have to eliminate the fluorine contained in the waste. This is because the fluorine forms strong complex with uranyl ions during the extraction process, and prevents from efficient extraction of uranium. In the current thesis؛ first, we examined the characteristics of the waste ... 

For optimum designing of dry friction clutch, we should taking into account a lot of parameters, in order to the clutch have good efficiency in torque transmission and power train. These parameters include: the type of friction plate and the mechanical properties, Clutch geometry, diaphragm spring and its ability to make pressure. In this project, the goal is the analysis of effect of different parameters in clutch's temperature distribution and effect of these issues in torque transmission. In next step, the clutch's temperature distribution analyzed by changing the friction plate (ceramic), pressure applied and relative round in order to gain optimum properties of clutch. These works done... 

Saline and fresh water lakes comprise a high proportion of the surface water resources and take effects from climate, hydrological, geomorphological changes and human activities in their basins. Variation in area of lakes causes changes in weather and local climate of their basins. Due to high environmental value of lakes and their particular effects on the ecosystem of the region, they have been always center of attention. Lake Urmia as the greatest lake in IRAN and the second largest saline lake in the world always has been considered by many researchers. In recent years Lake Urmia has had many changes such as decrease in area and level. Various factors such as climate change, periodic... 

Chronic wounds are among the serious injuries which have called the attention of scientists to invest in an effort to fabricate temporary skin grafts and wound dressing materials. One of the widely acceptable solutions to this obstacle is to design a bioactive scaffold capable of regenerating tissue as well as delivering active agents to the site specific area. To this end, natural biopolymers are considered as suitable candidates to be employed in regenerative medicine due to their excellent biocompatibility. In addition, nanoparticles possess special properties such as the ability in sequestering the drug release which make them promising candidates in the fabrication of the... 

Tissue regeneration by bio-compatible/degradable scaffolds is one of the widely used approaches in the field of tissue engineering. In this study, a thermoplastic starch based nanocomposite scaffold with gradient structure was fabricated by unidirectional freeze drying method. To increase the stability of the scaffold in the aqueous media, PVA was added to starch solution. Then, the PVA and starch molecules were cross-linked by adding citric acid to the mixture. On the one hand, to improve the mechanical properties of the scaffold, and control its bio-degradability on the other, cellulose nano-fibers were employed. Also, the bioactivity of the scaffold was induced by using hydroxyapatite... 

Waste management is one of the essential and basic utility services in 21st century, especially in rural areas. It includes different environmental, technical, economic, legal and social aspects which need to be considered in levels of waste generation, transport, treatment and disposal. Therefore, considering economic criterion in waste management programs, as the only one criterion, will result in environmental impacts in long-term and impose high costs to the society and the economy overall. The main purpose of this study is to develop a multi-criteria mathematical model, which take into account both economic and environmental criteria in order to present an integrated municipal solid... 

Recent studies have shown that comprehensive characterization of the behavior of infilled rock fractures under saturated and unsaturated conditions requires knowledge of morphological details of fracture surface, as well as state of stress of infill materials and their initial innate conditions (e.g., void ratio, water content, degree of saturation and dry density). This study presents the details and typical results from a new testing approach to study the hydro-mechanical behavior of the infilled rock fractures under different stress states and saturation conditions. The new testing approach incorporates the axis translation technique for suction control, a flow pump for the measurement of... 

Operational wastes of nuclear power plants are classified according to their radioactivity level & physical state. According to the radioactivity level, operational wastes are divided into low level waste (LLW) & intermediate wastes (ILW); & based on physical state they are divided into 3 groups of wet solid & liquid wastes, dry solid wastes & gaseous wastes.Bushehr nuclear power plants produce 1600 barrels of waste per year, among which dry solid waste is about 40 percent. According to the physical nature & treatment methods used, the dry solid waste is further classified into combustible, non- combustible, compressible & incompressible wastes.The purposes of dry solid waste treatment is... 

The development of novel three dimensional degradable porous scaffolds is of great interest for tissue engineering.silk ibroin has recently received intensive attention as a material for use in fabrication of 3D porous scaffolds beacuse of its excellent biocompatibility, physical and mechanical properties, and easy processibility. However, silk alone has no osteoinductive property and considerebely lower mechanical properties than native bone. In order to overcome this limitation silk fibroin can be combined with other materials.the properties of scaffold can be significantly improved and new features can be endowed by the second ccomposition. The present study deals with fabrication of... 

This research considers the wind effects on the thermal deficiency of natural draught dry cooling tower (NDDCT) using the CFD tool. To have a realistic study, the NDDCT of Shazand Powerplant, located in Shazand, Iran, is simulated as the sample cooling tower design points. Considering of Shazand NDDCT model, the mal-effects of local wind were studied against its thermal efficiency. As is known, the thermal efficiency of a NDDCT can be affected by local wind in either its upper (i.e., outlet section) or lower (i.e., the radiator section) parts. In this study, a full study is performed to quantify the mal-effects of local wind on either upper or lower parts of one tower. The results show that... 

The enviromental wind would cause serious drop in the performance of Heller cooling systems in thermal powerplants working on Rankin cycle. Therfore, it is necessary to consider the wind velocity in the design of such cooling tower systems. We use the computational fluid dynamics (CFD) and simulate the 3D buoyant flow passing through and over a heel cooling tower. We consider three different wind veocities of 0, 5 and 10 m/s in our simulations. In order to consider the low efficiency of the cooling system in efficiency drop of the main rankin cycle, we need to consider actual power generated by the powerplant generator, which is directly affected by the turbine back pressure. To connect the... 

Drying is one of the important downstream processes in the production of biotechnological products. The dryer design for heat-sensitive materials such as proteins requires special process considerations. In this study, a rotary dryer evaluated for drying protein products. The used liquid enzyme as model, a bacterial α-amylase, first, immobilized on sodium sulfate and sodium tripolyphosphate as carriers in a spraying mode and then, the obtained wet solid materials containing the enzyme, dried in a batch dryer. The performance of this dryer investigated to achieve suitable properties such as the enzyme activity and the final moisture content of product by changing the process conditions.... 

According to the climates of the country, using natural draft dry air cooling systems at the power plant is one of the proposed solutions for lower water consumption, but strong wind can make drop in performance of power plant cooling systems based on Rankine Cycle. This means that wind disrupted the order of the normal flow of air intake around the tower by creating areas of low pressure, preventing the flow of air into the cooling system. In the world, many researches and solutions have been proposed to solve the problem. The most common of these solutions is using of windbreaks as aerodynamic devices to compensate for the pressure drop in the cooling tower when the wind blows. But... 

Nowadays, cooling towers are widely used in power plants, refineries, petrochemicals and ventilation industries, but the water consumption of these towers is high and because of water crisis in Middle East and Iran, it is necessary to devise in order to reduce the water consumption of these towers. In this study separated hybrid cooling tower are used to investigate the water consumption at power plants. The rigorous Poppe method are used in order to estimate the exact amount of water loss due to evaporation in wet cooling towers. First, the effect of ambient condition, wet cooling tower cells and dry cooling tower size on the performance of hybrid cooling tower are investigated, then the... 

Enzyme immobilization/drying operations are among the important operations of many biotechnological industrial units. The enzyme used in this study is bacterial alpha-amylase, which is widely used in various industries, including detergents. The production of alpha-amylase enzyme contains a large percentage of water in its composition; therefore, a wet wall tower was designed to conduct the experiments to evaporate the water present in the enzyme liquor, analyze its effects on activity, and also to validate the device. The results showed that in a flow of air around 240m3/hr and ambient temperature of 20◦C, enzyme liquor has a 250% increase in biological activity, which indicates the...