@article { author = {Akgerman, A and Ghoreishi, S. M.}, title = {Dispersion Coefficients of Supercritical Fluid in Fixed Beds}, journal = {International Journal of Engineering}, volume = {13}, number = {1}, pages = {1-14}, year = {2000}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {The axial dispersion coefficient of hexachlorobenzene in supercritical carbon dioxide is investigated in a fixed-bed packed with glass beads. The on-line chromatographic pulse-response experiment is used in order to study the dynamics of a packed column under supercritical conditions. The radial dispersion is assumed negligible because of the packed column geometry. To estimate the axial dispersion coefficient, a pulse input of tracer/supercritical fluid (hexachlorobenzene/carbon dioxide) mixture is injected into the column and the effluent peak is analyzed using the moments of the chromatographic curve in the Laplace domain. The range of the operating conditions for temperature, pressure and flow rate of super critical fluid are 25-500 °C, 1200-4000 psia and 120-160 ml/hr, respectively. The experimental data indicate that the axial dispersion coefficient is a function of temperature, pressure and flowrate. The axial dispersion coefficient decrease with increasing temperature and increase with increasing pressure. This trend may be due to the increase of the density and viscosity of the super critical carbon dioxide. Further more, the axial dispersion coefficient increase with increasing interstitial velocity. These results suggest that the contribution by convection is more important than molecular diffusion under supercritical operations. In order to investigate the authenticity of the dynamic model as well as the extent of accuracy of the moment analysis which is used for parameter estimation, the experimental response peak is compared with the dimensionless theoretical (numerical solution) curve. The small deviation between the two curves is well within the range of experimental error of axial dispersion coefficient measurements.}, keywords = {Supercritical fluid,Axial Dispersion Coefficient,Carbon dioxide,Glass Beads}, url = {https://www.ije.ir/article_71245.html}, eprint = {https://www.ije.ir/article_71245_344ceb5a571ddfc3bd0401fb8ad5bed1.pdf} } @article { author = {Salehi, E. and Moghiman, M. and Noie, S.H.}, title = {Thermal Analysis of Shell-Side Flow of Shell-and-Tube Heat Exchanger Using Experimental and Theoretical Methods}, journal = {International Journal of Engineering}, volume = {13}, number = {1}, pages = {15-26}, year = {2000}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {In this paper the thermal behavior of the shell-side flow of a shell-and-tufe heat exchanger has been studied using theoretical and experimental methods. The experimental method Provided the effect of the major parameters of the shell-side flow on thermal energy exchange. In the numerical method, besides the effect of the major paramerers, the effect of different geometric parameters and Re on thermal energy exchange in shell-side flow has been considered. Numerical analysis for six baffle spacings namely 0.20, 0.25, 0.33, 0.50, 0.66, and 1.0 of inside diameter of the shell and five baffle cuts namely 16%, 20%, 25%, 34%, and 46% of baffle diameter, have been carried out. In earlier numerical analyses, the repetition of an identical geometrical module of exchanger as a calculation domain has been studied. While in this work, as a new approach in current numerical analysis, the entire geometry of shell-and-tube heat exchanger including entrance and exit regions as a calculation domain has been chosen. The results show that the flow and heat profiles vary alternatively between baffles. A shell-and-tube heat exchanger of gas-liquid chemical reactor system has been used in the experimental method. Comparison of the numerical results show good agreement with experimental results of this research and other published experimental results over a wide rang of Reynolds numbers (1,000-1,000,000).}, keywords = {heat exchanger,SHELL,Side Flow,Baffle Cut,Baffle Space}, url = {https://www.ije.ir/article_71246.html}, eprint = {https://www.ije.ir/article_71246_bbd324613e2b1535f1fde9ed7c34c84e.pdf} } @article { author = {Oskorouchi, A. M.}, title = {Effects of Degree of Consolidation and Anisotropic Consolidation Stresses on Shear Modulus and Damping Ratio of Cohesive Soils at Low Strain}, journal = {International Journal of Engineering}, volume = {13}, number = {1}, pages = {27-36}, year = {2000}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {During consolidation process of saturated cohesive soil the soil stiffness increases. Increase of the effective stress due to dissipation of excess pore pressure causes additional stiffness of soil mass. This phenomenon has a very important effect on the behavior of saturated cohesive soils during dynamic loading. In the current investigation the changes in maximum shear modulus. Gmax and damping ratio, D (as two important properties that affect on the dynamic behavior of saturated cohesive soils) at low shear strain are studied. Considering the properties of some typical soils which were used as a core of an embankment dam, a mixture of two different types of soil (SP + CL) was selected. A new resonant column system in shear mode was used in the shear strain range between?  l0-6% to l0-3 %. Then the mentioned soil properties were found in two different degrees of consolidation and three different confining stresses. It is concluded that increase in the degree of consolidation causes increase in Gmax and decrease in D. These changes completely depend on the consolidation stress. The results of this study can be used to determine the dynamic behavior of the core of embankment dams during dynamic loading based on its degree of consolidation in actual cases.}, keywords = {Shear Modulus,Damping Ratio,cohesive soils,Soil Dynamics}, url = {https://www.ije.ir/article_71247.html}, eprint = {https://www.ije.ir/article_71247_893c810d242b135058f9e44e21b694bb.pdf} } @article { author = {Salehi, M.}, title = {Delamination Wear Mechanism in Gray Cast Irons}, journal = {International Journal of Engineering}, volume = {13}, number = {1}, pages = {37-50}, year = {2000}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {An investigation of the friction and sliding wear of gray cast iron against chromium plated cast irons was carried out on a newly constructed reciprocating friction and wear tester. The tests were the first to be done on the test rig under dry conditions and at the speed of 170 cm/min, and variable loads of 20-260 N for a duration of 15 min. to 3 hours. The gray cast iron surfaces worn by a process of plastic deformation at the subsurface, crack nucleation, and crack growth leading to formation of plate like debris and therefore the delamination theory applies. No evidence of adhesion was observed. This could be due to formation of oxides on the wear surface which prevent adhesion. Channel type chromium plating 'picked' up cast iron from the counterbody surfaces by mechanically trapping cast iron debris on and within the cracks. The removal of the plated chromium left a pitted surface on the cast iron.}, keywords = {Wear,Delamination Wear,Gray Cast Iron,Chromium Plating}, url = {https://www.ije.ir/article_71248.html}, eprint = {https://www.ije.ir/article_71248_1ff9a110eda041da50b78226f7d9b8cc.pdf} } @article { author = {Farrahi, G. H. and Majzoubi, G. H.}, title = {Dynamic and Quasi-Static Tensile Properties of Structural S400 Steel}, journal = {International Journal of Engineering}, volume = {13}, number = {1}, pages = {51-60}, year = {2000}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {The study of mechanical behavior of the structural steel S400 under quasi- static and dynamic loading has been the subject of this investigation. In oder to obtain different stress - triaxiality conditions the specimens were notched with 1, 1.5, 2 and 3.5 mm notch radius. The results of fractography show as the velocity of tension increases, ductility reduces and a ductile-brittle transition occurs under certain stress triaxiality or strain rates. The observation of load-time history diagrams and SEM micrographs show that, as far as the fracture is ductile, any increase in velocity leads to the reduction of fracture load which is presumed to be due to reduction of plastic deformation. In brittle fracture, however, the velocity increase results in increase in fracture load which is thought to be due to micro-cracks formed at different level near to the fracture surface of specimens, the so called crack shielding and crack branching at high deformation velocities. Notch radius also proved to be highly effective on fracture mechanism which is due to notch strengthening. The change in grain size of some of the specimens shows that the ductile to brittle transition in fracture mechanism can be postponed by a suitable heat-treatment scheme up to a certain strain rate.}, keywords = {Dynamic,Behavior,Strain Rate,Fracture Mechanism,S400,Steel}, url = {https://www.ije.ir/article_71249.html}, eprint = {https://www.ije.ir/article_71249_7866284f712004dfecc5c8a7476d1283.pdf} } @article { author = {Esfahanian, M.}, title = {on Minizing Mechanical Stresses of the Rail Way Wheels}, journal = {International Journal of Engineering}, volume = {13}, number = {1}, pages = {61-76}, year = {2000}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {The purpose of this paper is to study the behavior of elastic-plastic stresses under severe drag braking. A railway wheel performs three tasks, aiding in trian movement, supporting the car load, and acting as a brake drum. Finite element computer programs are developed for elasto-plastic stress analysis. An attempt is made here to find an improved fillet profile of the wheel with the intention of minimizing high tensile mechanical stresses. Three new fillet profiles for the wheel are tested. A penalty function is used as a criterion for comparison of stresses between the new designs and the old design. The design with the least penalty is chosen to be the improved one.}, keywords = {Railway Wheels,Mechanical Stresses,Profile Optimization}, url = {https://www.ije.ir/article_71250.html}, eprint = {https://www.ije.ir/article_71250_dbd9420828e6cb36455eea8bfb85d31d.pdf} } @article { author = {Laderian, A.}, title = {Prediction of Temperature Profile in Oil Wells}, journal = {International Journal of Engineering}, volume = {13}, number = {1}, pages = {77-88}, year = {2000}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {A mathematical model has been developed to predict the temperature distribution in wellbores either offshore or inshore. It is incorporated the different activities encountered during drilling operations. Furthermore, the effect of drill collar and casings and bit rotating in a well during completion has been considered. The two dimensional approach is presented in the form of a computer program which is adopted for solution of the finite difference equations describing the heat transmission in the wellbore in the form of a direct solution technique. The power law mode l has been selected for drilling mud and its indices have been calculated. Comparing measured data, recorded for a period of 82 hours during different activities in a drilling operation for 15/20A-4, an exploration well in the Central North Sea with calculated results, show there is a good agreement between the prediction and measured temperatures in the wellbore.}, keywords = {Drilling,Casting,Mud,Formation,Temperature,transient,finite difference}, url = {https://www.ije.ir/article_71251.html}, eprint = {https://www.ije.ir/article_71251_400bbe3dcbc39bff50ea16d3c0290151.pdf} } @article { author = {Adibi, A. and SHARIFI, MJ}, title = {Semiconductor Device Simulation by a New Method of Solving Poisson, Laplace and Schrodinger Equations (RESEARCH NOTE)}, journal = {International Journal of Engineering}, volume = {13}, number = {1}, pages = {89-94}, year = {2000}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {In this paper, we have extended and completed our previous work, that was introducing a new method for finite differentiation. We show the applicability of the method for solving a wide variety of equations such as Poisson, Lap lace and Schrodinger. These equations are fundamental to the most semiconductor device simulators. In a section, we solve the Shordinger equation by this method in several cases including the problem of finding electron concentration profile in the channel of a HEMT. In another section, we solve the Poisson equation by this method, choosing the problem of SBD as an example. Finally we solve the Lap lace equation in two dimensions and as an example, we focus on the VED. In this paper, we have shown that the method can get stable and precise results in solving all of these problems. Also the programs which have been written based on this method become considerably faster, more clear. and mote abstract.}, keywords = {Finite difference method,Laplace Equation,Poisson equation,Schrodinger equation,Shotcky Barrier Diode,Vacuum Electronic Devices}, url = {https://www.ije.ir/article_71252.html}, eprint = {https://www.ije.ir/article_71252_0467fb339f049859f447c385fa68093e.pdf} }