Sirte University Scientific Journal

Determination of the Convection Heat Transfer Coefficients for Multiphase Flow on Different Sections of a Closed Piping System

Mahmoud Elsharafi — 2022-12-08

The continuous demand for petroleum-based energy as well as the increased need for geothermal energy has led to higher demands of piping systems transporting multiphase flows at high pressures and temperatures. As a result, the research of multiphase heat transfer throughout the piping system is inevitable, much of which the intricate details are still unknown. Multiphase flows and heat transfer have been studied in a wide range of applications such as mechanical, chemical, nuclear, and mineral engineering. The data from this project should prove useful in industries all over the world, especially industries that deal with refrigeration and with piping oil. Also, engines are massively important and their efficiency is becoming more prominent than ever before, and this research could aid in their efficiency. Also, the longevity and performance of these multiphase-flow piping systems, amongst other things, depend greatly on the heat transfer rates they obtain. In this experiment, results were found showing the correlation between the orientation, input temperature, input air pressure, and flow rate of the liquid, with the flow rate showing to make the largest difference.

Best Performance of Reactor Controllers Using Stochastic Optimization Method

Yousif A. Alsadiq — 2022-12-08

Based on the mass and energy balances for the reactor and heating system, a mathematical model for a continuous stirred tank reactor is created. The concentration is changed stepwise, and the reactor's temperature is gauged as a result. This study compares the use of PI, generic model control, and fuzzy logic controllers on the system with the aim of evaluating each one's performance in light of the integral of the absolute error that is produced. The controller's settings are adjusted using a simulated annealing technique. However, in order to have a fairly comparison The range of the PI and Generic model controller’s gains are increased as well as the simulated annealing solution numbers, on the other hand the number of membership functions for variable and solution numbers are increase for fuzzy controller. MATLAB/SIMULINK has been used to implement the control and simulation investigation.

Concentration of Lead, Cadmium, Zinc and Iron in maternal blood and umbilical cord in Zeliten city, Libya

Adel. M. Mlitan — 2022-12-08

The present study was carried out to determine the lead, cadmium, zinc and iron concentration in maternal and umbilical cord blood. Samples were collected from Zeliten delivery hospital in the period from February to April 2018. A total of 70 pregnant women participated in this study, We compared the concentration of Lead, Cadmium, Zinc and Iron in maternal blood and umbilical cord. There is significant difference in maternal blood concentration of iron compared with umbilical cord blood iron concentration (P value 0.047), while there is no significant difference found in concentration of other studied metals (Zn, Fe, Cd).

Hydrological Simulation of Wadi Al-Kouf, Libya

Aiesha Omar Ijdayyat — 2022-12-08

Surface water scarcity poses a serious threat to sustainable development and one of the main restrictive factors of economic growth in Libya. However, the average rainfall records ranged in north of Libya from about 200 to 500 mm, with a maximum of recording on the regions of the Green Mountain where was about 850 mm. Digital Elevation Model (DEM), The Soil Conservation Service- Curve Number (SCS-CN) method and the Watershed Modeling System (WMS, Version 8.1) has been applied to analyze and simulate the surface runoff storms of Wadi Al-Kouf using Hydraulic Engineering Center model (HEC-1). This model was used to simulate runoff volumes and hydrographs. Al-Kouf watershed is located in the central part of Al Jabal Al Akhdar of north Libya. The investigated basin is enclosed approximately between latitudes 32.5° N and 32.8° N and longitudes 21.4° E and 22.00° E. The rainfall data for period (2002-2003) were used for the analysis and estimation of the direct runoff for the study area. Different simulated cases have been studied which showed a good agreement compared with the measured results. The main purposes for embarking on the study determine the amount of runoff and peak flow rate generated from rainfall storms and harvest runoff water surface, by suggestion a set of weirs at various locations in the strategic parts in the study basin may be built to avoid future flooding of the cities and the roads. In this study, we were able to know peak of discharge and volume of each basin outlet and find out where to put weirs. The simulation results reveal that about 190 Million cubic meters of surface water could be harvested.

Anchor Angle and its Role on Stability of Anchored Retaining Walls

Mohamad Gabar — 2022-12-08

The purpose of this research is applying PlAXIS 2D in modeling of an anchored retaining wall with different combinations of behavior of the anchored wall and prepare data base that can serve the design requirements of anchored retaining walls in Libya. The structural design of the anchored wall by PLAXIS finite element software, considers soils on the back and front of the wall as well as the soil under the wall. So, this research takes into account the effect of soil under wall on wall behavior. The effect on wall is studied in terms of wall displacement, wall bending moments, wall shear forces, and soil stresses. The effect of anchor angles by using varying soil properties, wall & anchor properties, and loads behind the wall on the wall behavior has been investigated as well. The results proved the applicability of Plaxis model in responding to different combinations of wall and soil parameters, and showed different structural behavior by the anchored wall with every change in wall and soil parameters. So, findings corresponding to different combinations of parameters were prepared for the sake of any related future research.

Upgrading the seismic capacity of RC buildings using chevron buckling restrained braces

Fozeya O. Algennay — 2022-12-08

Many RC buildings do not meet the lateral strength requirements of current seismic codes and are vulnerable to significant damage or collapse in the event of future earthquakes. Several systems are available for seismic strengthening of RC buildings such as enlargement of the structural members and adding new structural shear walls.

In. the past few decades, buckling-restrained braces have become popular as a lateral force resisting system because of their capability of improving the strength, the stiffness and the energy absorbing capacity of structures. This study evaluates the seismic upgrading of a 6-story RC building using chevron buckling restrained braces. Seismic evaluation in this study has been carried out by static pushover analysis and time history earthquake analysis. Ten ground motions with different PGA levels are used in the analysis. The mean plus one standard deviation values of the roof-drift ratio, the maximum story drift ratio, the brace ductility factors and the member strain responses are used as the basis for the seismic performance evaluations. The results obtained in this study indicate that strengthening of RC buildings with buckling restrained braces is an efficient technique as it significantly increases the PGA capacity of the RC buildings. The results also indicate the increase in the PGA capacity of the RC building with the increase in the amount of the braces.

The use of BRBs in one bay in each of the perimeter frames of the RC building results in a significant improvement to the base shear capacity of the RC building. In the current study, an increase in the base shear capacity up to150% from the base shear capacity of the original RC building has been achieved by the BRBs.

The Effect of Polypropylene Fiber on the properties of fresh and hardened self-compacting concrete (SCC)

Ghusen M. AL Kafri — 2022-12-08

The Self-compacting concrete (SCC) defines as a highly flowable, non-segregating concrete that fills uniformly and completely every corner of formwork by its own weight and encapsulate reinforcement without any vibration, whilst maintaining homogeneity. This research conducted to evaluate the effects of polypropylene fiber addition on characteristics and properties of SCC mixes in fresh and hardened state of SCC. In this study, the concrete mixes were added with polypropylene fiber of 0.0 %, 0.05%, 0.1 %, and 0.15 % Of volume fraction, mineral admixture i.e., silica fume 10% of weight of cement and chemical admixture i.e., Super Plasticizer 1.2% of cement and silica fume is used with constant w/(c+s) ratios which equal 0.49. For determining the self-compact ability properties like passing ability, flowability, viscosity, and segregation resistance the following tests such J-ring, Slump flow, V-Funnel and L-Box tests were performed. After 7 and 28 days of curing, cubes, cylinders, prisms, compressive, splitting and flexural strengths were tested. Tests results indicate that polypropylene fibers tend to reduce the flowability and passing ability but will increase viscosity and segregation resistance of SCC. Furthermore, it can be concluded that polypropylene fiber reduces deformability of SCC in the fresh state. After7and 28 days of curing, concrete specimens’ tests indicate that polypropylene fiber addition up to 0.15% of volume fraction tend to improve the compressive strength, tensile strength, and flexural strength of hardened SCC. It also can be suggested that polypropylene fibers allowed to be added into SCC mixes up to 0.15% by volume of concrete.

Numerical Analysis of Skirted Strip Footing Behavior Nearby Unsupported Slope

Aziza Milad Elgerari — 2022-12-08

The soil around foundation plays a very critical role during its behavior. The skirts form an enclosure in which soil is confined and works as a unit with the overlie foundation to transfer superstructure load to soil essentially at the level of skirt tip resulting increase in the bearing capacity and lowering in the settlement of the structure. The present research focused on the analysis of skirted strip footing adjacent to unreinforced slope using a finite element software PLAXIS 2D. The variables which are considered in the current study are depth of embedment of the footing (De) in terms of height of slope (H), the ratio of distance of strip footing from crest to the width of the footing (b/B), and the ratio of depth of skirt to width of the footing (ds/B). The skirt configuration is provided on one side vertical skirt, both sides equal vertical skirt and unequal vertical skirt. The numerical study shows that the using of structural skirts with adequate depth in the conjunction of strip footing to slope crest has a substantial increase in the ultimate load bearing capacity of strip footing. The enhancement in ultimate load bearing capacity of skirted strip footing increases with increasing skirt depth, embedment depth of footing and crest distance of unsupported slope. The two sides equal vertical skirted strip foundation shows significant increase in ultimate load bearing capacity and decrease in settlement.

Effect of Video vs. Book-Guided Tutorials on CAD Learning performance

Mosa Allafi A-Rahman — 2022-12-08

This research aimed to investigate the effect of video vs. book-guided tutorials on CAD Learning performance of new CAD learners in terms of (time and accuracy) and psychological attitude (understanding, motivation and mental effort). 32 new architecture students participated in the study and were randomly assigned to two groups. The presentation of the CAD tutorial differed between the two groups according to the independent variables to be addressed (book and video). The research materials and tools represented in accomplishing the CAD tasks, which requires mastering some CAD skills prescribed by the computer design approach, such as drawing walls, doors, windows, ceiling, and 3D views. The results indicated that the use of video in CAD learning increases the learning time and enhances the accuracy of drawing more than the book. In contrast, the use of the book shortens the learning time, but at the expense of the accuracy of drawing compared to the video. The results also revealed that students were in favor of video capabilities for learning CAD lessons in terms of understanding, motivation and less mental effort to comprehend.