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Showing 3 results for Subject: Fluid Mechanics

Mahmoud Salari, Mohammad Mohammadtabar,
Volume 1, Issue 1 (4-2019)

ABSTRACT: the empirical correlation for prediction of the onset of boundary layer transition, presented previously by Taghavi et al., was extended by taking into account both the effects of the streamwise pressure gradients and the freestream turbulence intensity. The correlation was derived based on experimental data of transitional boundary layers subjected to different freestream turbulence intensities and streamwise pressure gradients, obtained by authors and other researchers. The author’s experiments were carried out in two different free stream turbulence levels and four different pressure gradients. A single hot-wire probe was used for measurements of instantaneous flow velocities within the boundary layer. Experiments were conducted in an open circuit wind tunnel of suction type. For each pressure gradient in a distinct free stream turbulence level, the mean longitudinal velocity and root mean square, RMS, of the velocity fluctuations were obtained at several streamwise locations. Experimental results were used to determine variations of streamwise skin friction coefficient and boundary layer shape factor versus the local Reynolds number. Based on the available measurements and mathematical models, an improved empirical correlation was developed. Comparisons with other existing empirical correlations show that the new correlation was more consistent with experimental data.
Amin Emami Razlighi, Mahsa Asadi, Behnam Nasrollahzadeh,
Volume 1, Issue 1 (4-2019)

The rapid advances in human societies over the past decades have resulted in fast development of steel, cement, and other industries. Cement is one of the most important industries which plays a significant role in the development and prosperity of any country and worldwide. On the other hand, cement factories are among the major environmental plights and source of contamination. Accordingly, one of the main issues of these factories is controlling and preventing excessive emission of contaminants. Electrostatic precipitators are among the most important devices for controlling air pollution. One of the most important influential parameters affecting the efficiency of dust collection in the design of the electrostatic precipitator is the migration velocity. In this research, this parameter was studied in the electrostatic precipitators of ELEx, Hamon, and FLSmith companies, which are responsible for collecting the dust from Clinker coolers in cement factories. The results of the research suggested that the range of this parameter under the mentioned conditions was obtained as 8.7-11.5 Also, it can be stated that with elevation of the efficiency of mechanical dust collection of the equipment, one can achieve a better efficiency. This can be realized by properly exploiting chemical engineering, mechanical engineering, electricity engineering, as well as the experiences of scholars, thereby reducing costs, increasing the useful lifetime of equipment, and preventing environmental pollution.
Behnam Nasrollahzadeh, Reza Elyasi,
Volume 1, Issue 1 (4-2019)

Producing cement with appropriate quality and by spending the minimum cost, applying solutions including process optimization and use of grinding aid are suggested. This paper compares and investigates the effect of process optimization and use of grinding aid on the operational capacity and blaine of final product in two cement mill departments in a cement plant. The results of a specific grinding aid test and its effect on the quantity and quality of the final product were compared with the results obtained from process optimization of cement mill lines 1 and 2 of a cement plant including optimization of the arrangement and tonnage of the charge of balls. The results suggested that the operational capacity of cement mill of lines 1 and 2 when optimizing the process conditions increased by around 9.4 and 15%, and the blaine of the final product of the department rose by about 4.6 and 4.3% respectively compared to the case of using the grinding aid. It should be noted that performing the grinding aid test in relation to the initial conditions only resulted in enhanced operational capacity of cement mills, and had no significant effect on the parameter of quality (blaine). On the other hand, performing the process optimization had positive effects on both quantity and quality.

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پیشرفت ها در مکانیک جامدات و سیالات Advances in Solid and Fluid Mechanics.
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