Basrah Journal for Engineering Sciences

The solar chimney is a natural draft device that uses solar radiation to provide upward momentum to the in-flowing air, thereby converting the thermal energy into kinetic energy through an air turbine which in turn can be converted into electrical energy. The main parts of the solar chimney power plant are a large circular solar collector, a tall chimney, and an air turbine. In this paper, a theoretical study was performed to evaluate the performance of a solar chimney power plant system in Basrah City, where sunny days and solar radiation are high. A mathematical model was developed to study the effect of various parameters on the output power of the solar chimney. I1 was found that the output power depends strongly on the chimney tall and the difference between the collector air temperature and the ambient air temperature as well as the outside heat transfer coefficient, which essentially depends on the wind speed.

A mathematical model is presented for a solar updraft tower power plant with a water-storage system. This model is developed to evaluate the effect of geometrical parameters of the solar tower power plant and thermal storage system as well as the wind velocity on the power production of the plant. The analysis is based on variable solar incident radiation along the day. The results show that the tower tall, the tower diameter, the wind velocity, and the collector diameter have a significant effect on the power production while the thickness of the water-storage layer is shifted the peak value of the output power far away from mid-day and more smoothing the output power curve. The results are compared with other models and experimental data. A good agreement is obtained.

In this paper, a finite element method program under domain loading and plain strain conditions was developed and applied in the evaluation of the stress intensity factor in opening mode ( K 1 ) in two dimensions of crack problems. Two types of crack problems are analyzed and verified: first, cracked rotating disc made from bi-directional fiber reinforced material composite, and second crack blade made from bi-directional fiber reinforced metal matrix composite. It is found that the finite element method under domain loading is a good tool for the analysis of composite material. The simulation is accurate in comparison with that obtained from the extrapolation method. The strei-s intensity factor for fiber-reinforced metal matrix composite is larger when obtained from fiber-reinforced material under same condition.

Electromagnetic flowmeters have proven their merit in· measuring the flow rate of conducting liquids in fully-filled pipes. In contrast with most of the published works about the electromagnetic flowmeter, the attentions were focused in this work on the use of these devices in partially filled pipes. In this application, these devices suffer from the problem of different outputs with different liquid levels for the same flow rate. We studied whether the process of changing the distribution of the magnetic field through the measuring section improves the flowmeter performance against this drawback or not. An adaptive numerical mesh was used in predicting the flow-induced signal and its response to the liquid level. The induced signal was assumed to be picked up by a pair of point electrodes tested for different angular positions. The results showed that the performance of the electromagnetic flowmeter in partially filled pipes could be appreciably improved by making the magnetic field progressively decrease from the top to the bottom of the flowmeter. When the lower magnet coil is excited by a current one-half lower than the upper coil, together with two-point electrodes placed at 22° below the flowmeter horizontal centerline, the flowmeter performance offers more stable sensitivity.

This paper is concerned with a stress analysis in a bearing under unbalanced forces of the journal. Some aspects of mathematical modeling of rotating structures were considered. "Finite Element Method'' is fom1ulated for modeling rotating structures. As an application, a test rotor mounted on two-lobe hydrodynamic bearings is presented. Unbalance response calculations for various unbalanced magnitudes are ca1Ticd out in the bearing location. The bearing coefficients were found at a rotational speed of 4,000 rpm. An accurate identification of bearing force parameters, i.e. stiffness and damping coefficients is presented by a classical linearized model. The bearing support forces in flexible rotor-bearing systems are presented as a function of the unbalanced response of the journal. The calculation of the bearing stress due to rotor balance is carried out using ANSYS. The ANSYS program gives good aid in understanding the ~tress analysis in the bearing under the action of journal rotation.

This research makes a two-dimensional model for a cold flat rolling process using the ANSYS program. The contact pair is used between the contact surfaces using the boundary condition of the surface-to-surface contact. The process of symmetric rolling is tested for two types of materials (aluminum and mild steel). The rolling force for (1%) to (25%) reduction of a slab of dimensions of (200 * 10) mm using (Avitzur) theoretical equations and ANSYS. The radius of the rolls for aluminum is (75) mm and that for mild steel is (300) mm.
The numerical results were compared with (Avitzur) theoretical equations. The comparison shows that the values of forces calculated using (Avitzur) theoretical equations are accurate enough up to (5%) reduction, and the numerical results proved its accuracy up to (25%) reduction.
The study shows that forces increase as a result of increasing the rolling metal area at the entry rate. The angle of the neutral point was also studied in this work and it is found that it decreases with the increasing reduction rate, due to an increase in the cohesion area on the sliding one within the rolling process while the theoretical results failed to calculate the angle of the neutral point correctly.

Brazing is one of the best methods of graphite-to-graphite or to-metal joining. But the major problem associated the graphite brazing is the poor wetting by the conventional molten fillers. For this reason, scientists have produced a special filler metal based on active elements that interact with graphite to form carbides. Also, recently another technique to overcome the wetting problem was introduced by H. Ohmura and T. Yoshida. It included inserting an intermediate layer of pure iron foil inside the copper filler. In the present work, another filler combination of Cu/ steel/Cu foils is proposed as a new filler technique for graphite brazing. It was found that it produced a succeeded joint with good properties consisting of a columnar phase which resulted from the partially dissolution of iron in molten copper. Additionally, the increasing of brazing time caused reducing the thickness of the steel central layer and increasing the thickness of the columnar phase layers. The x-ray diffraction test developed that the joints contained two carbide types, iron, and copper-free elements.

The objective of this research is to characterize a new technique of copper filler addition to the brazing joints of 316L stainless steel to overcome the wetting problem between them. This technique includes the electrochemical deposition of copper on the stainless steel joint parts to ensure optimum coinciding, minimum oxidation during brazing heating, and consequently good wetting and bonding. An evaluation of the present technique and a comparison with the traditional one were performed. The samples were tested to find the shear strength, microhardness, microstructure, and x-ray diffractometry. In general, the present new electro-deposited fillers were better than the traditional filler in producing perfect joints with higher shear strength. On the other hand, there was an opportunity to produce acceptable joints with electro-deposited fillers in an air environment.

In this work, the efficiency of the double Gauss quadrature method, used to integrate over a rectangular clement in 3D BEM, has been investigated. The efficiency of a quadrature or integration scheme is investigated by estimating the critical ratio for which the absolute relative error of the numerical integration is less than 1x10. As small as the critical ratio is, the quadrature is more efficient. Also, special transformation techniques have been introduced and used to increase the accuracy and efficiency of double Gauss quadrature, especially for near singular cases, where the source point is very close to the element under consideration. Three types of kernels were considered, weak, strong, and hyper singular kernels which can be encountered in the integral equation of 3D elastodynamics BEM problems.

The aim of the present study is to perform an analytical simulation for the single-effect LiBr- water absorption refrigerating system (ARS) in order to scan for all possibilities of operating the cycle among the most available operating variables to obtain the best performance and determine what are the proper parameter needed to be changed so that the refrigerator can operate using ambient air instead of water and cooling tower accessories to dissipate the heat at the condenser and absorber. The COPs of the cycle were obtained as a function of the different temperatures of the cycle and solution concentration. The performance characteristics of the cycle were examined by changing the temperature of the heating source supplied at the generator, and the temperatures at the condenser, absorber, and evaporator. It can be concluded that the concept of an air-cooled absorption chiller is feasible with a coefficient of performance of 0.43 to 0.79 depending on the evaporator temperature for any cooling capacity in some applications, where the chilled water supply temperature is not necessary to be too cold.

The ability to predict the performance of a petroleum reservoir is of immense importance for the petroleum industry. Numerical simulation is the most powerful tool that can be used for reservoir performance prediction. In the current study, a new simulator has been designed for two-phase compressible oil-water flow through compressible porous media. The new simulator is able to treat the frontal advancement and the high rate of change region by static and dynamic local grid refinement. A new approach is proposed in this study to trace the frontal advancement. The proposed simulator has been applied to several field reservoir cases and show good performance.

The present work aims to study the performance of the reverse osmosis process at the Al-Dura power station. The selected membrane that is used in this work is made from polyamide (thin film composite membrane (TFC)) constructed as a spiral wound module. The basic advantages of this type of membrane are the higher productivity compared with the total volume of the module, and the stability of the polymer towards the chemical effect.
It was found that recovery percentage (or product rate), rejection percentage (or solute concentration in product), and concentration factor decrease with increasing operating time for the reverse osmosis unit, whereas, the operating pressure for the reverse osmosis unit increases with time. Maximum salt rejection percentage and maximum recovery percentage were determined to be 96% and 75% respectively for polyamide membrane.

A novel iterative method for the restoration of gray-scale blurred images is presented. The method is an enhanced modification of the Fixed-Phase Iterative Algorithm (FPIA). A blurred image is enhanced by the Laplace operator during the FPIA method on each iteration. This modification is originally supported theoretically by a derivation of some iterative deblurring methods that are based on the enhanced version of the blurred image instead of the blurred image itself only.
The modified fixed phase iterative algorithm (MFPIA) method is examined to restore some Gaussian and motion-blurred gray-scale images. The restored images via this proposed method are compared with the original FPIA method. From the comparison, it is apparent that the MFPIA method is better from a human visual measurements point of view with less number of iterations. In addition to that benefit, the restoration by the FPIA method results in images of bad quality even with a high number of iterations.

In this paper, the design of a linear phase FIR digital filter using the Frequency Sampling method is presented. Such a design is achieved with a reduction in the maximum step-band ripples utilizing optimal transition-band sample value throughout the use of the Golden Section search method for single transition samples and with the aid of the Steepest Descent method for double transition samples. The realization requirements of such filters are reduced by the use of a new analytic design. The reduction can be increased to 50% of the whole filter structure. Therefore, the designed FIR filter offers global properties, minimum stop-band, minimum pass-band, average deviation, and reduced structure complexity.

Observing the local engineering projects done nowadays shows the weak application of quality assurance. In this paper, a questioner paper was designed depending on ten proposed points which could be assumed to represent the steps of quality assurance in any engineering project and could be used to measure the quality degree in it. The questioner has two sides, the first measures the importance of the proposed ten points, and the second measures the application of these ten points in the local engineering projects. A weak understanding of quality assurance and contracts that don't contain points forced contractors to follow ISO quality conditions, also low efficiency of inspection instruments and team was found. The paper suggests that the curricula of all engineering studies must include quality assurance subjects. The importance of the proposed points was found to be (78%) while the quality assurance in the local engineering projects was found to be (37%). Quality in a bridge in Diwaniya city was calculated and found equal (49%).