المستودع الرقمي لـجامعة طرابلس

Abstract

Deposition of undesirable materials on water wall side of boiler tube that are operated under forced circulation boiling conditions can cause serious trouble in steam boilers. The present study is concerned with the scaling characteristics of water in the boilers. The effects of heat flux and water velocity were evaluated for water having a total hardness and calcium hardness in the range (TH= 380 to 390 ppm asCaCO3 ) and(CaH= 250 to 298 ppm asCaCO3) respectively. The heat flux ranged from (1.05 x 105) to and water velocity in a vertical annular test section range from 0.51 to 0.75 m/sec (1.67 to 2.5 ft/sec) . The test section consisted of an annular duct 0.050 m (2.0-in) O.D. and 0.033 m (1.33-in ) I.D. A 0.30 m (12-in) section of the concentric core of the annulus was electrically heated. Hot water at 97.0 (370.1) was circulated through the annulus where boiling occurred on the heated section. The temperature range at the Surface of heated section in the annulus was from (105 - 118 ). The results of five tests are reported in this study. The fouling resistance vr. time curves reached an asymptotic value and the average of fouling resistance for Runs (1-5) had been plotted. Chemical analysis of scale deposits indcated that Calcium carbonate and Silica were the man Constituents. At constant surface temperature an increase in velocity from 0.51 to 0.75 m/sec (1.67 -2.5 ft/sec), caused about a 20 percent reduction in the asymptotic fouling resistance.
عادل محمد شنقير (2008)

Abstract

During the last years there has been an increasing consciousness of the environmental problems, created by the use of fossil fuels in electrical power generation consumed by converting cooling systems. In addition, the use of common working fluids (refrigerants), with their ozonedepleting and global warming potential, has become a serious environmental problem. This underlines the need to implement advanced, new concepts in building air-conditioning. The most common global type of thermally driven technology to produce chilled water is absorption cooling. For air-conditioning applications, absorption systems commonly use the water/lithium bromide or ammonia/water as working pair of fluids. The objective of this study is to establish a fundamental basis for further research and development within the field of solar cooling. In this study, an overview of possible systems for solar powered refrigeration and airconditioning systems will be presented. The concept of the ‘Solar Cooling Path’ is introduced, including a discussion of the energy source to the collector. Brief information and comparisons of different absorption refrigeration cycles are also presented. A solar-driven absorption refrigeration system has been selected as a case study for a further detailed investigation. A low temperature heat source can be used to drive the absorption refrigeration cycle, making the system suitable for integration with solar thermal collector. The Transient System Simulation program (TRNSYS) and Engineering Equation Solver (EES) simulation tools are used to model and analyze the performance of a solar-driven absorption refrigeration system. Analysis of the absorption cycle system is initiated by steady-state analysis. A modeling of single effect water/lithium bromide absorption cycle was constructed to study the effect of the operating variable on the system performance and to determine the optimum operating conditions for the absorption cycle. This model was developed by Engineering Equations Solver program (EES). In practice, the ambient conditions and solar radiation are not constant. Therefore, a dynamic analysis is useful for determining the characteristics of the system during the entire year, and dimensioning the important components of the solar collector subsystem, such as storage tanks and collector area. The overall solar absorption cooling system has been simulated by the TRNSYS program with a typical meteorological year file containing the weather parameters for the capital of Libya, Tripoli. Finally, a parametric study was carried out to investigate the influence of key parameters on the overall system performance of solar absorption cooling system and hence to improve and optimize the system design. Results from the parametric optimization indicated that with an area of 130m2 of flat plate collectors with an inclination of 32° and 3.5m3 of storage tank is achieved to cover the demand of air conditioning of a 35kW absorption chiller.
إبراهيم محمد علي الطويري (2011)

Abstract

Electric insulators are one of the main parts of over head Transmission lines, they must meet two requirements, first is the electric insulation for the conductors, and the second is to provide mechanical support for the over head lines. Insulators are subjected to various electric stresses of different origin such as operating voltages and an electric stroke waves due to Lightning storms. Therefore the insulators must perform well under all weather and environment conditions. In addition some times degradation occurs in the insulators performance due to accumulation of different types of pollutions on its surfaces. This project deals with two samples of silicone rubber insulators Have been exposed to the natural pollution for 6 years in continuously energized line working in Libyan transmission network. The test line is connecting between Khomes power station to Khomes switching substation it is 8.5 km long, the site is considered to be the most polluted site in Libya .Several tests have been done on this type of insulators to the effect of Libyan Environment on these insulators to decide if this insulator is suitable for working in the Libyan electrical grid.
عبدالمولى بشير على اوحيده (2010)

Abstract

Erosion wear is recognized as an engineering problem for slurry handling equipments. It plays an important role in design and operation of slurry transportation systems. The present work reports experimental and theoretical investigations of erosion wear of carbon steel and stainless steel in sandwater mixture. However, carbon steel (AISI-CS1060) and stainless steel (AISI-SS316L). They have been chosen as target materials, and then studied the effect of various parameters that may leads to good understanding to the erosion behavior of ductile materials such as impact angle, particle velocity as well as erosion time on erosion wear. The impingement jet erosion test rig built at our laboratory in order to carry out the experimental results. Aluminum oxide (Al2O3) is used as erodent particles after it mixed with water for slurry preparation at various impact angles of 15°, 30°, 60° and 90°, the solid concentration range of (10-30) wt%, for sized ranging between of 800µm to1700µm in the velocity range of 5 m/s to 24 m/s, with periodic time of 10 minutes at room temperature. The data points that collected in this work showed that the experimental values are agreement with the ductile erosion behavior for both materials, also showed that the erosion rate increasing linearly with increases in impact velocity and erosion time, also showed scars were characterized by an elliptical shape at 15° and 30° whereas a nearly circular shape was observed at 60° and 90° due to the horizontal component of velocity at shallow angles has value more than the normal component of velocity whereas in contrast at high angles.
فاضل رزق شحات (2014)

Abstract

Estimation of wind characteristics is considered as the first essential step to evaluate a wind energy project based on information about all aspects of the implementation and operation of the project. It's therefore necessary to have detailed knowledge of the wind to design a suitable wind turbine for a certain zone and also to estimate its performance accurately. The first step in this thesis is study the wind energy and wind assessment in the selected site (Zuara) based on the available wind data, which are obtained from the representative meteorological station. The second step in this thesis is study is to design a suitable horizontal axis wind turbine. Design (HAWT) to achieve satisfactory levels of performance starts with knowledge of the aerodynamic forces acting on the blades. The blade element momentum theory (BEM) is applied for HAWT blade design and to predict the performance of the rotor. A computer program for HAWT blade design and its performance analysis is belt. The input of this program is: power required from a turbine, number of blades, design wind velocity, design tip-speed ratio and properties of the selected airfoil. While the output are: blade geometry parameters (chord and twist distribution), power, torque and thrust coefficients versus tip-speed ratios. This study indicates that capacity factor on the Zuara site equal 3 and it is seen that possible to designed wind turbine to extracting the power from the wind with satisfactory levels of performance in the selected site
فرج الأخضر شنشن (2014)

Abstract

Five symmetrical Schiff base ligands[four bi-dentate and one tetradentate(L3- L7)] and two un-symmetrical bi-dentate and tri-dentate (L1-L2) ligands with the Nitrogen and oxygen chromophore were isolated inpure form and good yield. The ligands were fully characterized by elemental analyses, melting point, IR, H1- &13C- NMR, and mass spectra.The Schiff bases L1 and L2 were successfully coordinated to Pd(II) and VO2+ ions respectively and these complexes were characterized using elemental analyses, IR and mass spectra. The interesting result by mass spectrum of VO2+ complex of L2 shows parent peak at 524 confirming that the formula of the complex as [VOL2(ac.ac.)2H2O] in which the complex has an octahedral geometry.The symmetrical Schiff bases (L3-L7) were also successfully coordinated to Nickel (II), Copper (II), Lead (II), Cadmium (II), and Mercury (II) ions to form their corresponding complexes. The total twenty five metal (II) XI Schiff base complexes of (L3-L7) were isolated. These complexes were characterized by elemental analyses, melting points, IR, mass spectra technique. 1H &13C-NMR Spectra in DMSO d6 for Pb, Cd, and Hg complexes show the expected number of peaks with deferent chemical shift comparing with the free ligands in the same solvent. The interesting result by mass spectrum of Ni(L7)2 complex compred with of L7 spectra shows parent peak at 977 confirming that the ligand L7 has lost one proton to give the desire complex in square planar geometry.
حميدة أحمد سالم العباني (2015)

Abstract

For this study, two identical single-effect of single basin solar stills are designed, fabricated, tested, and evaluated, where one of them is employed alone which is referred to as “passive still”, while the other is coupled to a flat plate solar collector introducing what so called the active still. Both are installed at the same site in Tripoli-Libya and they are oriented due to south. Measurement of various temperatures, solar intensities, humidity, wind speed and distillated water production are taken each hour for several days of August under various operating conditions. Two operational modes are considered; each of the passive and active stills is operating for the whole day. These tests were performed using seawater and water basin different depths. The water production of the active still is reported to be 6.6 L/m2.day which is higher than that of the passive still by 56 per cent approximately. The maximum daily efficiency is calculated to be 24 per cent approximately for the active still system while it is 14 per cent approximately for the passive still. Yet, the still thermal performance seems to have a complex function of geometrical, constructional, and operational conditions, site characteristics and layout details.
صالح أحمد سرابيط (2010)

Abstract

Forging in a flat and overlapping dies have many industrial applications, and many parts can be produced, parts with ends of different shapes, and study of such process is important to understand the mechanic, and effect of different variables, Specimen shape, die geometry. In this work, a study forging of copper specimens between flat dies and overlapping dies having cylindrical, rectangular and square cavities, were fixing cross-section area in all specimens and changing the shape of cross-section area. Load displacement relationships were presented and study the effect of friction and constrained volume shapes on flow behavior and effect of (D0/H0) ratio are also investigated. Double extruded part with a hub are produced by the combined forward and backward extrusion forging process, and comparison between the results of constrained volume with double extrusion part was made.
مصطفي حسين المغربي (2010)