Tikrit Journal of Engineering Sciences

An industrial scale falling film reactor (FFR) using gaseous SO3/ liquid Alkylbenzene as operating system- is analyzed for multiplicity and stability. The analysis has shown that up to 5 steady state solutions may exist. The existence of a highly multiplicity states is explained by the coupling between absorption and reaction. The system kinetic parameters have found to play an effective role on the stability behavior. An analytic solution is found for a special case of the liquid reactant in excess, this solution is performed by using eigen analysis. A mathematical procedure is also introduced to estimate the bifurcation points.

CHEMCAD process simulator was used for the analysis of existing benzene separation column in LAB plant(Arab Detergent Company/Beiji-Iraq). Simulated column performance curves were constructed. The variables considered in this study are the thermodynamic model option, top and bottom temperatures, feed temperature, feed composition & reflux ratio. Also simulated columns profiles for the temperature, vapor & liquid flow rates compositions, were constructed. Four different thermodynamic models options (SRK, TSRK, PR, and ESSO) were used, affecting the results within 1-25% variation for the most cases. For Benzene Column (32 real stages, feed stage 14), the simulated results show that bottom temperature above 200 oC the weight fractions of top components, except benzene, increases sharply, where as benzene top weight fraction decreasing sharply. Also, feed temperature above 180 oC shows same trends. The column profiles remain fairly constant from tray 3 (immediately below condenser) to tray 10 (immediately above feed) and from tray 15 (immediately below feed) to tray 25 (immediately above reboiler). Simulation of the benzene separation column in LAB production plant using CHEMCAD simulator, confirms the real plant operation data. The study gives evidence about a successful simulation with CHEMCAD.

In this work a program is developed to carry out the nonlinear analysis (material nonlinearity) of prestressed concrete beams using tendons of carbon fiber reinforced polymer (CFRP) instead of steel. The properties of this material include high strength, light weight, and insusceptibility to corrosion and magnetism. This material is still under investigation, therefore it needs continuous work to make it beneficial in concrete design. Four beams which are tested experimentally by Yan et al. are examined by the developed computer program to reach a certain analytical approach of the design and analysis of such beams because there is no available restrictions or recommendations covering this material in the codes. The program uses the finite element analysis by dividing the beams into isoparametric 20-noded brick elements. The results obtained are good in comparison with experimental results.

The dual filter was tested in this study to improve the performance of the filtration process in water treatment plants. Porcelanite rocks were selected to be the dual media with sand in the experimental work. The work required installing a pilot filtration unit in the location of the filters in one of the water treatment plants. The pilot filtration consists of three plastic column filters, acting parallel and simultaneously. The first contains 70 cm sand, the second and third were dual filters (porcelanite with sand) of different types. The dual media was tested at different filtration rates (5, 7.5, 10, and 15 m/hr). The results showed that the dual filters had better performance than sand filters and reduced the specific deposit ( ) and the breakthrough index (BI). In the dual filters the specific deposit was about (16 to 65 %) less than in sand filters and the breakthrough index (BI) was specified weak for rates 5 and 7 m/hr, light at 10 m/hr, and medium at 15 m/hr..

A mathematical model was formulated using the absorption of carbon dioxide by monoethanolamine amine as an absorbent in a falling film reactor. A program wrote in Fortran language was used to obtain these profiles via using of multi grid method through programming of kinetic and thermodynamic equation and physical properties of the studied system. Through the formulated model film thickness, surface temperature, velocity, concentration and temperature profiles were obtained. The mathematical analysis validated by a test run in a Baiji refinery through intrusion of liquid flow rate, liquid concentration and gas fraction. In this study we have four factors as independent variables ,they are mole fraction of hydrogen sulfide in gaseous mixture (Y) (0.05, 0.75 and 0.1), molar concentration of absorbent (monoethanolamine) (CMEA) (0.05, 0.075 and 1 M), volumetric flow rate of liquor MEA (QMEA) (5, 10, 15, and 20), and its temperature (T) (30, 35, 40, 45, 50 and 55 C).

The last stage endured on obvious erosion especially the front and the end of the blade. The erosion caused the appearance some cracks in this place. These remarks coincided with the theoretic al results, which were acquired according to the condition of the turbine of station which showed that the droplet, which collided with the blade ends, caused high pressure on the surface of the blade and caused the occurrence of the corrosion. The danger of the erosion unavoidable due to its relationship with tae station efficiency and the only to avoid that is the use of the blade made of erosion resistance ingots.

In this paper a laboratory work was performed to study the effect of bridge piers inclination and surface roughness on scour pit dimensions. Fifty four experiments were conducted using three different sizes and inclinations Pier models fixed in a sandy bed channel. First, the axis of the pier was parallel to the flow, then it was inclined by 30° and finally by 45°. Each model was tested under three different flow discharges for a period not less than two hours and at the end of each experiment the dimensions of the scour pit were measured. The same experiments were repeated after roughening the surface of each pier by fine gravel of 2mm in diameter to increase its roughness. The results of the experiment showed a clear reduction in scour pit dimensions after increasing pier roughness, the percentage of decreases in scour depth was between 2 % and 61%, while the scour length decreased between 2.5% and 22%, and finally the width of scour decreases was between 3% and 19.7%. The results also showed that the inclination of pier’s axis produced an increase in scour pit dimensions. Finally, the empirical relationships of the results showed that it’s possible to explain the relation between the flow discharge and each of scour pit dimensions by a simple linear equation, where the determination coefficient were more than 0.94 for all relations.

Solid Detergent is one of the Economic materials and Environmentally friendly method towards enhancing properties of concrete. Lightweight, slow reaction and anti acid concrete can achieving by using this materials, so many test made to validate the advantage and disadvantage ; initial and final hardening time for cement mortar and compressive strength of concrete, also anti acid test made for cement mortar. The results of tests show this materials are suitable for achieving the purpose to lightweight, slow reaction additional anti acid concrete.

The present study is conducted by exposing copper weldement specimens which were prepared by oxy-acetylene welding operation for copper tube by using tin-bronze alloy as a filler metal , to salty and acidic aqueous solutions containing respectively (0.5, 1.5 and 3) wt% NaCl and (0.5, 1 and 2) wt%H2SO4 . The corrosion behavior of weldements showed a general decrease in corrosion rates in salty solutions with increasing of exposure time . The same thing happened to the weldement specimen which was exposed to the acidic solution containing (0.5) wt%H2SO4, while the corrosion rate of the weldements which exposed to the acidic solution containing (1 and 2)wt%H2SO4 was dropped during the first (288 hr) of exposure then a relative increase was observed by increasing the exposure time. Also the results of the calculated total corrosion rates (CrT) indicated higher value for the weldements exposed to acidic solution if they compared with those values obtained with salty solution for (696 hr) exposure. Further more; the examinations by optical microscope for the weldements indicated presence of pitting corrosion at welding zones by exposing the weldement to both salty and acidic solutions, while the general corrosion had a moderate appearance of the cupric part for weldements tested by these two solutions.

In this paper, numerical solution is presented for the steady state, two dimensional natural convection heat transfer from two parallel horizontal cylinders enclosed by circular cylinder. The inner cylinders are heated and maintained at constant surface temperature, while the outer cylinder is cooled at constant surface temperature. Boundary fitted coordinate system is used to solve governing equations. The vorticity-stream function and energy equations is solved using explicit finite deference method and stream function equation solved by successive iteration method. (20)Deferent cases are studied cover rang of Rayleigh number from (1,000) to (25,000) based on the inner cylinder diameter. These cases study the effect of the varying inner cylinders position horizontally and vertically within outer cylinder on the heat transfer and buoyancy that causes the flow. Outputs are displayed in terms of streamline, isothermal contours and local and average Nusselt number. The results showed that the position of the inner cylinders highly affects the heat transfer and flow movements in the gap. At low Rayleigh numbers the average Nusselt number increases with increase of horizontal distance between inner cylinders but the state is reversed at high Rayleigh numbers, while the average Nusselt number is increases with inner cylinder moving down at all Rayleigh numbers. The optimal position of inner cylinders for maximum and minimum heat transfer is located at each Rayleigh number so can be employed in isolation process or cooling process.