Iraqi journal of mechanical and material engineering

During this research, simulation of the candidate materials done as insulted brick for the furnace wall. Results were obtained through the use of simulation by COMSOL multiphysics program. Showed results obtained from this program, Al2O3 brick has high deformation value 2.34 *10-4 m and the maximum vonmises stress value 267 Mpa focused at the edges of the fifth slice. Vonmises stresses various along the slices of bricks of Al2O3-MgO, Al2O3-ZrO2 and MgO-ZrO2. Zirconia brick has 486 Mpa the maximum value of the vonmises stress. ZrO2 brick has low value 1.486 * 104 w/m2 of the total heat flux, while maximum value of the total heat flux occur in the Magnesia brick which has 2.267 * 105 w/m2. Structural brick of Al2O3-MgO has low total deformation value 7.987 * 10-5 m and low value of the maximum vonmises stress 133 Mpa. These data supporting use this brick of Al2O3-MgO as best candidate for the furnace wall without failure during the service.

This research presents a mathematical model that established for evaluating the effect of the radial strain on the performance of an electrooptic modulator using MATLAB simulations. It can be used the variable values for the forces applied with in specific area for the crystal\'s arm for an electro optic modulator and this is under the condition to the value of visibility factor can be improved and using this technique it will evaluate the effect of radial strain. So, this model leads to enhancement the performance an electro optic modulator using MATLAB simulations. Finally, visibility factor of an electro optic modulator versus radial strain can be evaluated for different values of force and which considers important factor on the performance of an electro optic modulator for the modern communication system.

The experimental analysis includes a patient lying on an operation table, surgical staff members, and surgical lights above the patient. The cold clean air is supplied to the room through grilles from ceiling diffusers and exhausted through low side walls. The first aim of the experimental study is to investigate the validity of air distribution within operation room and the effect of using the air filtering on the air flow distribution. Different air distribution system to what exists in the optical operation room, is also investigated by locating the inlet at the upper part of a side wall, while the exhaust grilles were in the lower part of the opposite side. From this study, it was found that the temperature and relative humidity in the surgical zone are 21.3oC and 49.3% in the optical operation room. While, the values in the experimental operation room are 23.6oC and 45.3%. These values in both operation rooms are in the acceptable range of the surgical conditions as well as for the carbon dioxide. Therefore, it can be using the wall air supply system in the operation room with good conditions for the surgical work.

Despite increasing demand for the application of three – dimensional extrusion of various shaped sections through continuous dies, so far little work has been done by general analytical and numerical analyses to predict the total extrusion pressure for the extrusion of polygonal sections from round billets through polynomial streamlined dies. For effective die design, efficient design method and the related method of theoretical analysis are required for extrusion of complicated sections. A systematic method for the die surface representation using blending function and trigonometric relationships is proposed in which smooth transitions of the die contour from the die entrance to the die exit are obtained. The upper bound extrusion pressure is obtained by derived a general velocity and strain rate felids. The effects of area reduction, the optimum die length, the shape of streamline function and frictional conditions are also discussed in relation to the relative extrusion pressure. Another advantage of the present work is that it could easily be applied to the extrusion of many different shapes just by defining the entry and exit sections functions and putting them into the general formulations. The results obtained in this work were compared with the theoretical results of other workers and found to be in highly compatible. The extrusion process is also simulated using the finite element code, ANSYS (V 14.0) in order to assist the mathematical solution and to show the stress and strain distributions for the products when the strain hardening effect taking into the account.

The design of the labyrinth seals depends on two main factors, namely, the reduction of leakage loss and the avoidance of rotor system instability. The most important parameter affecting the prediction of leakage mass flow rate of fluid through the labyrinth seal, namely, the carry over coefficients. Hence the computational fluid dynamics (CFD) and model has been used to predict the carry-over coefficient of flow through teeth on rotor straight through labyrinth seal. The mathematical model proposed through this work has been solved using the finite volume technique using a FLUENT commercial computer program. The effect of turbulence, seal geometry such as (teeth width, clearance, and pitch cavity) and shaft rotational speed have been taken into consideration. A prediction equation for the carry-over coefficient of the labyrinth seal has been proposed through this work. The prediction equation of carry over coefficient has been found to be a function of (C/S), (W/S) and Reynolds number. It can be concluded from the results that obtain here that the carry over coefficient which describe the labyrinth seal efficiency is highly affected by clearance to pitch ratio (C/S) , while the tooth with to pitch ratio (W/S) has a secondary effect on carry over coefficient. The results obtained show that the carry over coefficient is increased about 42% with increasing of the (C/S) from (0.0075 to 0.0375). While this coefficient is decreased by 9% at Reynold’s number more than 8000 with increasing of (W/S) from ( 0.0075) to (0.5). The effect of rotation has been studied on the carry over coefficient; therefore, the results showed that the carry over coefficient decreases with 10% after a certain value of rotation which is equal to (10000 rpm).Verification for the prediction models of the present work has been carried out by comparing some of the results obtained through this work with the experimental results published by Scharrer (1988) , Eser (2004) and the CFD analysis of Vamshi (2011). The results obtained through the present work found to be in a good agreement with the results of other workers.

The effect of nanoparticles on the heat transfer of the fluids becomes one of the most interesting fields for researches. Metallic and nonmetallic materials are used to enhance the thermal performance of the fluids. In this work, an attempt was made to extend the work in this field to study the effect of addition of copper oxide nanoparticles on the transient behavior of free convection in horizontal cylinder. The dimensionless form of the energy and the momentum equations was solved using the commercial package COMSOL 3.5. A constant wall temperature CWT boundary condition was subjected to the surfaces of the cylinder. The lower half of the walls temperature was always higher than the upper one. The effect of volume fraction of nanoparticles on the stability of the transient behavior of the heat transfer and the fluid flow was examined. Also the effect of Rayleigh number on the velocities, temperature and Nusselt number are shown graphically. It is found that not only the onset of instability of the natural convection but also the type of the steady state profiles of temperature and velocities were affected by the existence of the nanoparticles. A phase plane plot was used to analysis the steady state types of dynamic behavior of the nanofluid natural convection under the CWT boundary condition.