Sharif Digital Repository

In water service processes, tubular heat exchangers are commonly used to provide a heat transfer medium for cooling or heating of which both are subject to fouling of heat transfer surfaces. The deposit would dominantly build up in form of fouling, crystallization, and or particulate fouling depending on the operating and surface conditions. This, in turn, may result in more demand for excessive energy consumption due to higher pumping requirements, as well as for offsetting the impact of fouling. Introducing the subject of the on-line condenser tube cleaning system as a most effective way of encountering with deposits and its components, the difficulties encountered during operation and... 

The synthesis and usage of nanoscaled TiO2 accompanied by the photocatalytic activity were experimented through a systematic research. The synthesis was based on the sol-gel method at low temperatures and atmospheric pressure. In recent years, many endeavors have been made so as to enhance the efficiency of TiO2 photocatalytic activity. The studies show that the inclusion of SiO2 into the TiO2 can give rise to the photocatalytic activity relevant to the derived composite Nanoparticles with regard to the pure TiO2. In this study, the production of TiO2-SiO2 Nanocomposite layers was proceeded via the sol method and the effect of SiO2 increasing and its amount in the primary solution on the... 

Nowadays by fast growing the population and development of countries, the demand of energy is increasing rapidly. Solar energy is one of the most reliable and environment friendly source of energy. Photovoltaic modules (PV) are such a solar systems that is able to convert solar energy into electrical energy. However, some parameters such as increasing cell temperature and dust accumulation can reduce the PV modules efficiency. Increasing the cell temperature reduce the capability of electrical production of cells and dust accumulation is an obstacle for solar radiation absorption. As a result, in this research tempt to solve these problems by building a new device for PV modules. In this... 

Zinc oxide thin films due to special specification and properties have variable application in different industries. Recently because of wide application of zinc oxide doped SiO2 in optoelectronics and sensors, lots of investigation have been focus on it. Meanwhile due to the SiO2 hydrophilic properties, doping of ZnO with SiO2 can improve self-cleaning properties zinc oxide membrane.It this project zinc oxide and ZnO doped SiO2 thin films with different composition were made by sol-gel and dip-coating process used for coating of mentioned sol over the quartz surface(15*25 mm). At first point different sol with different components was mixed with each other to make composite films but due to... 

In this research, TiO2 nano-particles were electrophoretically deposited on the FTO glass to produce self-cleaning property. Two type of suspensions with different TiO2 nano-powders were used. Merck and fabricated by sol-gel route, TiO2 nano-powders were utilized in suspensions and Conductivity, pH and zeta potential of suspensions were determined. Electrophoretic deposition of two kind of suspensions was performed in different voltages of 10, 30 and 60V (for 10s) and room temperature. TiO2 coatings were sintered in 450oC for 1 hour. The phase transformation of TiO2 films were measured using XRD. Morphology, average particle size and thickness of TiO2 films were analyzed using FESEM... 

Using of solar spectrum because of its potential for producing green energy is the topic of interest in Current decade. The goal of current research is increment of efficiency by using of a single layer and double layer semiconductor TiO2 – ZnO coating that has been synthesized by sol-gel process, which have anti-reflation and self-cleaning properties that in short time and long time for durability of solar systems can be useful. In first step of this research the single layer TiO2 (by 85nm thickness, measured by FE-SEM) and ZnO (by 65nm thickness) coating with different concentrations of pore forming agents ( plironic f127 for TiO2 and CTAB for ZnO) in coating sol examined and observed... 

In this study, industrial steel (DIN 17135) underwent a new purification process with the aim of removing non-metallic inclusions and producing clean steel. Samples of steel were levitated in synthetic slag from the CaO-CaF2-Al2O3 system by an electromagnetic field. The effect of time, temperature and slag composition factors on the inclusions content of sample has been investigated. The images of the optical microscope were evaluated according to the ASTM E 45 standard, which according to the extracted results, the removal process was done to the desired extent. On the other hand, as the time and temperature of the process and the weight percentage of CaF2 increase, the number and size of... 

All societies need energy to meet the basic needs of the people and to carry out the production processes. From 1850 onwards, the global use of fossil fuels (coal, oil and gas) for energy production increased, leading to a dramatic increase in the emission of carbon dioxide (CO2) into the atmosphere. Rising carbon dioxide and other greenhouse gases in the Earth's atmosphere and seeing adverse effects such as global warming have prompted the international community to replace fossil fuels with clean energy as much as possible. Geothermal energy as one of the clean, sustainable and extensive sources can be one of the available solutions to meet this need.Numerical modeling of geothermal... 

Asdefined by Nicholson [W. K. Nicholson. (1977). Lifting idempotents and exchange rings. Trans. Amer. Math. soc. 229: 269-278] an element of a ring is clean if it is the sum of a unit and an idempotent, and a subset of is clean if every element of is clean. In this thesis some like-cleanness properties are introduced and relations between them are investigated.Many equivalent conditions for cleanness of reduced, semiprimitive Gelfand and functional rings are obtained,and finally these results are applied in the rings of continuous functions  

In this study, TiO2-SiO2 nanocomposite films with different amount of SiO2 were prepared by sol-gel process and were coated onto stainless steel 316L. The effect of addition of various amounts of SiO2 in the precursor solution on the structure, morphology, photocatalysis, photo-generated hydrophilicity, self-cleaning property and mechanical properties of TiO2 thin films and corrosion behavior of AISI 316L stainless steel substrate, was investigated. For this purpose, X-ray diffraction, Fourier transform infrared spectroscopy, water contact angle measurements, UV spectroscopy, field-emission scanning electron microscopy, atomic force microscopy, depth-sensing indentation technique supporting...