نشریه انرژی ایران
سال یازدهم شماره 2 (پیاپی 41، تابستان 1387)

A functional layer of titania membrane on alumina substrate is successfully fabricated, via the sol-gel processing method, and the photocatalytic activity of the final membrane is determined. Results show the average particle size of 55.6 nanometers of the final titania sol. Microstructural investigations of the final membrane show the thickness of 930 nm for the titania layer. The layer is crack-free, it shows that the preparation procedure is optimum. The photoactivity of the membrane is measured via the degradation of methyl orange in the presence of ultraviolet radiation. After 9 hr radiation, methyl orange is degraded 27%. Parameters such as calcination time and temperature that affect the photoactivity of the mambrane are investigated.

Although pulsed columns are used in both packed and sieve plate, but more investigations had been done on the pulsed sieve columns. Dispersed phase holdup is one of the most important parameter used in design of pulsed packed columns. This work is the result of experiments on a glass pulsed packed column on a laboratory scale with 2 in. diameter. The variation of the dispersed phase holdup with height and the effect of mass transfer were studied experimentally in this work. As shown later, with height increasing, dispersed phase holdup is increased. When mass transfer is from continuous phase to dispersed phase holdup is decrease. When the direct of mass transfer is from dispersed phase to continuous, vice versa, holdup decreased with increasing of height.

Widespread application of central cooling systems in socio economic sectors and also in different climates of country needs thorough investigation to present a pattern for determination of effect of consumer type, climate and cooling capacity. In this paper, central cooling systems have been analyzed by “Annual Equivalent Method” and usage of them has been investigated from the consumer, energy supplier and national point of views. The systems, which are prioritized, contain air cooled and water cooled vapor compression chillers and five kind of absorption chillers including hot water single effect, direct fire, steam single effect,double effect and warm water single effect. The appropriate system with regard to cooling capacity, climate and consumer type are the results that will be presented in this paper.

The reduction of fossil fuels and environmental problems have made researchers look for a substituting fuel that is renewable and produces less pollution. The biological fuels, especially biodiesel, are probable to get common as suitable fuels that are adjustable with the present diesel motors. Biodiesel is an alkyl ester that is obtained from vegetable oils and is identical to diesel #2, but because it causes less pollution it is counted as an environment-friendly fuel. vegetable oils, waste vegetable oils from cookery, and animal fat are sources of biodiesel production; however, these sources are not able to account for human requirements. As microalgaes grow rapidly and can produce large amounts of oil, they can be taken into account as a renewable source for biodiesel. Microalgaes exploit the sunray and carbon dioxide to photosynthesize and to produce oil, but compared with vegetable oils they have a higher percent of oil. These micro-organisms are able to grow in various environmental conditions and can be produced artificially and via photobioreactors. The process of producing biodiesel from microalagaes has three stages: growth, oil extraction and oil exchange into biodiesel, all of which are dealt with in this study.

Wind Towers are small towers, which have been used for the natural ventilation of the buildings in hot, arid regions of Iran since many years ago. When the wind blows, air enters the channel of wind tower, it transfers the heat to the internal surface of wind tower walls and finally the cool air comes into the building.The most important advantage of wind towers is air conditioning and air cooling without any use of electrical energy. In this study, the performance of the tallest wind tower of the world (wind tower of Dolatabad garden in city of Yazd) is analyzed by employing a CFD package. The temperature, perasure and velocity disturbutions of air at different cross-sections and along the column of wind tower are investigated. Heat transfer, fluid mechanics and thermodynamics principles are applied in order to evaluate the performance of wind towers. Finally, the results are presented.

In this study the elements of the steam cycle of Loshan natural gas power plant have been analyzed from the exergy point of view and two parameters, waste and exergy efficiency, which are important measures for system analysis, are calculated for steam cycle elements. The results indicate that the boiler, in which heat transfer and combustion processes take place, is the main factor in waste of exergy.

Rapid development of gas industry such as other energy sectors, has been affected from important technologies introduced from the middle of twentieth century. GTL technology to convert natural gas into fuel and liquid chemical products contributes to improving natural gas transportation to remote areas, increasing added value, recovering associated gas and converting it to high quality products as well as meeting environmental objectives. For these reasons, countries with large natural gas reserves have been encouraged to use and develop GTL. In this respect, this paper tries to present a brief introduction of GTL process as well as five executive approaches for desirable deployment of this technology. These approaches include establishing GTL plants with development and operation of gas fields, establishing independent GTL plants, establishing GTL plants beside power plants, establishing GTL plants beside LNG plants, and operating small GTL projects at the oil fields. Conditions and characteristics for investment, technical knowledge transfer and different contract formats such as foreign direct investment (FDI), license agreements, joint venture, buy back and build-operate-transfer (BOT), for five preceding approaches are also analyzed and compared. Finally, this paper introduces approaches for implementation of the prementioned contracting formats from techno-financial aspects.