Year:2000 | Volume:34 | Issue:3 (69)|Papers Count:11

In this research paper, the increase of sulphur trioxide formation (SO3) is studied during its combustion in a mixture of n-pentane with air which contains various percentages of sulphur dioxide (2.5-20%), in ratio of n-pantane. The simulation of its kinetic with computer, facilitates the study of the hypothesis precision, for a mixture of a low quantities of sulphur dioxide.

One of the most important parameters in designing pulsed columns is overall mass transfer coefficient based on dispersed phase. Some of the proposed equations for calculation of mass transfer coefficient based on dispersed phase are: 1-Newman's equation or its modified one by substituting effective diffusivity or overall effective diffusivity instead of molecular diffusivity.2- Kronig and Brink's equation or its modified form. 3- Handlos and Baron's equation or its modified form. Different correlations have been proposed for effective diffusivity by Temos, Davies. Steiner, Johnson and Homielec. Lochiel and Calderbank. In this work column height is calculated at different operating conditions using above mentioncd mass transfer. Coefficient equations. Comparison of the column actual height with calculated height from above mentioned models shows that the average percentage deviation is too fluctuated. Calculated heights using equations of Newman, Kronig and Brink, Temos, Steiner are much higher than actual height and. calculated heights using Handlos and Baron's equation is less than actual height.Also results show that the average percentage deviation of height predicted by equations of Johnson - Hamielec and Lochiel - Calderbank from actual height is up to 34% and 64%, respectively. Finally results show that as internal circulation increases column internal decreases.  

Air mixed liquid containing vessels are frequency used in chemical process industries. In many processes such as in bioreactors, gas/liquid reactions and processes where mechanical agitation may not be possible, air (gas) agitation is used to mix the content of the vessel. Such processes frequently involve consumption or generation of heat which must be transferred by flow of a suitable service fluid on a jacket or a coil. Heat transfer coefficient of the process side of such systems may be an important consideration on the design of aerated vessels. This coefficient depends on many factors one of which is the flow rate of the air. In this experimental study the effect of varies parameters on this coefficient is investigated. An empirical equation relating Stanton number to Fraoud and Reynolds number has been derived based on these findings which agrees well with similar correlations in the literature. This equation can be a useful tool in the design and evaluation of such heat transfer systems.

Upgrading of Ilmenite and Titanomagnetite concentrates of Kahnooj ore by Slag-making route was investigated. The effects of the process parameters and pre-oxidation of the starting materials on the formation of slag, separation of slag from pig iron and distribution of elements have been studied. The results revealed that the time and temperature of reducing and melting steps, along with the type and amount of flux are the most important parameters of the process and have a significant effect on the characteristics of the products. For instance in the presence of 5 wt% of dolumite, the quantity of vanadium oxide in slag decreased on increasing the time and temperature of melting steps. The results also indicate that the pre-oxidation of the concentrates has no considerable effect on the process.

For deep drawing of sheet metals and converting them to irregular shaped prismatic shells which have been designed before, the initial blanks should be correctly designed. Otherwise, final products will not be sound. The design of the initial optimum blank is, therefore, very important. The initial blank could be designed experimentally or numerically. Numerical methods have very advantages. In this paper by using slip line field theory and geometrical characteristics of die, just like angles and radii of corners, sides' length and height of draw, a new method for initial blank's design will be presented. Then by using a new applied method, an equarial orthogonal net will be constructed around the die. Using constructed net, metal flow paths and blank's movement contours will be obtained. The punch stroke will then be calculated, using material properties and equarial orthogonal net, during the different stages of drawing. According to the mentioned methods, a package has been written that in a very short time, can predict optimum blank shape, metal flow paths, blank's movement pathes and punch load, with appropriate percision.

In this study tribological properties of pulsed electrodeposited crack free chromium and DC electrodeposited hard chromium coatings were studied, by using a dray reciprocating pin on plate wear testing machine. The crack free coatings showed higher wear rate and coefficient of friction than the hard coatings. The wear mechanism in these coatings was mainly adhesive, while the mode of the wear in the hard coatings was mainly abrasive.

Swirl injectors have been used widely in the combustion chamber of rockets with liquid propellants. These injectors are able to atomize he fuel and the oxidizer in the range of 20-80 Microns which highly creates an efficient combustion. The injectors create spray cones which their impacts cause more atomization of the drops and their uniform distribution in the combustion chamber. The distance between the injectors and their configuration is very important in the atomization and the uniform distribution of the drops. In this experimental study, the effect of the distance between the two injectors and their impact have been studied with PDA.  

In this paper a mathematical model for simulation of natural convection in a solar dryer which consists of solar collector, drying enclosure and the chimney has been investigated. The temperatures along the solar collector as well as drying enclosure were obtained by numerical solution of intercoupled momentum and energy equations. The variation of the air temperature in the collector and across the drying enclosure is incorporated in the prediction of the thermal buoyancy effect. The results show that with in creasing the collector length the air temperature at the exit of collector is increased. The latter decreased while the chimney height increased. It is found that the mass flow rate of air is described by collector length and chimney height. The air temperature along the dryer enclosure has been measured and is compared with numerical solution results. The agreement between experimental and numerical results are quite  satisfactory.  

The effect of wall slip on the entrainment of non-Newtonian fluids is investigated onto a sheet withdrawn vertically from a bath of liquid. For a wave-free two-dimensional laminar film, the equations of motion are shown to reduce into a single third-order nonlinear ordinary differential equation incorporating slip velocity as an adjusting parameter. Film thickness values obtained by numerical solution of this equation are found to become virtually consistent with experimental data provided that wall slip being occurred. With wall slip as the boundary condition, it is shown that for purely-viscous power-law fluids, better predictions can be obtained for the film thickness if inertia terms are included in the equations of motion.