Tikrit Journal of Engineering Sciences

Powders have been mixed as (Al with 99% purity ≤53μm particle size, Cu with 99.5% purity ≤53μm particle size, Mg with 99.5% purity ≤53μm particle size, Y2O3 with 99.9% purity ≤53μm particle size, Gr with 99.9% purity ≤53μm particle size). one set of composite samples was prepared by addition (3wt%Gr) to metal powders shown above. For the each sample of composite varying (Y2O3) weight percentage as: (Al 2024-3wt%Gr-XY2O3) was added x=(0,2,4,6,8)(wt%) the other set of composite was in opposite. Well mixed samples was pressed uniaxial with (700Mpa) and (30sec). the compacted samples were sintered at (6000C) for (2hr). Results have shown an increase in bulk density by (5.3%) for (Al 2024-3wt% Gr-XY2O3) with the increase of reinforcement until (8wt%) of (Y2O3), while bulk density have been reduced for (Al 2024-3wt%Y2O3-XGr) with (5%) with the increase of (Gr) weight content in the composite. An increase in real porosity was noticed with the increase of (Y2O3) with (8wt%) (11.9%) for (Al 2024-3wt%Gr-XY2O3) but this was less in comparison with (Al 2024-3wt%Y2O3-XGr) were porosity increase with the increase of (Grwt%) up to reduced (18.5%) at (8wt%Gr).Mean value was of micro hardness decreased gradually with the increase of (Grwt%) to reach (19.4%) reduction at (8wt%Gr) in opposite the micro hardness mean value increased by (20%) as (Y2O3wt%) increased to (8wt%).Compression strength have was increased by (51%) as (Y2O3) content increased from (2-8)(wt%) for (Al 2024-3wt%Gr-XY2O3) composite, while it was decreased by (48%) with the addition of (8wt%) graphite to (Al 2024-3wt%Y2O3-XGr).The content of (Gr) had higher effect on wear rate than (Y2O3) where the wear rate decreased by (59.7%) and (41%) for composite samples respectively, within the limits of addition in the current study.

The research is about designing and building up an evaporative cooling system, working by two- stages evaporative cooling system using outer air (pure air). The system is founded by designing and making a heat exchanger of orthogonal flow from Aluminum sheets of (30*60*40) cm, which represents the first stage of the system (indirect stage). The second stage (direct stage) of the system is represented by making an equipment of air washing (cylindrical) with (45 height, 60 width, 3 thickness) cm. The cooling system pulls outer air by a Centrifugal fan. The air passes through the heat exchanger pipes to be cooled tangibly (without moistening). Then it goes over the equipment of air washing to be cooled and cools the specified space. Computer software was designed by FORTRAN Language (FORTRAN 90) to predict the evaporative air cooler performance to know the proper environmental and design conditions of the system. Some variables were made to study their effect on the thermal performance of the system. The studied variable is to change the volumetric flow rate of air from (750 cfm) to (2000 cfm) of the dry side, and from (750 cfm) to (2500 cfm) of the wet side. The pipe length was changed from (20 cm) to (45 cm), and its diameter from (0.5 cm) to (3 cm). Those were the design changes. On the environmental changes, we studied the effect of changing the temperature on the dry or wet bulb of the system. The study is taken place in Tikrit University (34. 35N; 43.37 E), to determine the suitability of the weather conditions of the region for the work of the system. It was taken place in the late August for two consecutive days, with readings of 24 hours. The results show that the best quantity of the air supplied, which represent the best performance of the system (750 cfm) and (1000 cfm) for the wet side when the diameter (1-1.5 cm) and length is (45 cm). The results show also the possibility of the work of this system for the region mentioned because it is characterized by its hot and dry climate in the summer, as the efficiency of evaporative evaporator increases the hot and dry environment by 80%.

This research deals with production of light weight aggregate concrete by using clayey stone aggregate, normal material (cement , sand) and some of mineral admixtures (fly ash and steel fiber ). Many trial mix were doing some of these by weighing ratio and others by volumetric ratio . We get light weight aggregate concrete (LWAC) with 24.92 N/ mm2 compressive strength and we improved mechanical properties by adding same percentage of fly ash and steel fiber (0.5 ,1 ,1.5) % of each other as a percentage weighing ratio of cement content . compressive strength increased with (7.8 , 5.2 , 2.9) % , splitting tensile strength increased with (20 ,16.71, 12)% and flexural strength increased with (24.5 , 17.9 , 8) % when adding (0.5 ,1 ,1.5) % of each steel fiber and fly ash respectively. The practical results of the current study indicates that the using clayey stone to produce (LWAC) is success and we can improved mechanical properties of this (LWAC) was produced in this research by adding fly ash and steel fiber with previously percentage.

The present study uses the multivariate statistical techniques by applying the Factor Analysis (Principle component method) to explain the observed water quality data of Tigris river within Baghdad city. The water quality was analyzed at eleven different sites, along the river, over a period of one year (2017) using 20 water quality parameters. Five factors were identified by factor analysis which was responsible from the 72.291% of the total variance of the water quality in the Tigris river. The first factor called the pollution factor explained 34.387% of the total variance and the second factor called the surface runoff and erosion factor explained 11.875% of the total variance. While, the third, fourth, and fifth factors explained 10.213%, 8.861% and 6.956% of the total variance and called pH, Silica and nutrient factors, respectively. Multivariate statistical techniques can be effective methods to aid water resources managers understand complex nature of water quality issues and determine the priorities to sustain water quality.

In this research, the load-deflection behavior is explored for concrete beams reinforced with FRP bars (polymer reinforcement). An experimental test is done for a total of five beams subjected to 4-point loading. The tested specimens are of dimensions; 2100 mm (length), 200 mm (width) and 300 mm (depth), while the used compressive strength for concrete is f’c = 60 MPa. Four beams were longitudinally reinforced by various CFRP rebar numbers, and the last beam was reinforced only by steel bars as control beam. Relationships for load-deflection were drawn and the influence of several factors was debated on this relationship. It was exhibited that the failure of FRP reinforced samples was generally ruled by the concrete strength. When the ratio of reinforcement rising by 50%, 100% and 150%, the ultimate load increased by 15%, 29% and 38%, respectively, while the recorded deflection at ultimate load decreased by 7%, 16% and 24%, respectively. For the ultimate load of the studied beams, outcomes exhibited that the equations of the American code ACI 440.1R give very close values with the test values, while they give very conservative values to the deflection at ultimate load which are smaller than the test values by about (37%-45%).

The study aims to show effect of adding the circular perforated plates in sedimentation basin in horizontal position on the efficiency of the sedimentation basin as was the use of perforated panels with circular holes and placed inside the sedimentation basin and took two levels of turbidity of the water 125 and 150 NTU respectively in the Tigris river during the preparation of the study with variable hydraulic load and the efficiency was calculated at each case of plates in the basin where the variables that were adopted is the number of perforated panels so that the ratio of the area of holes/total area of panel is 20% , and also variation in water turbidity levels and the hydraulic load. The result showed a significant decrease in the output turbidity levels from sedimentation tank with the use of perforated panels at the raw water turbidity 150 NTU and hydraulic load between 0.9 and 1.2 m3/m2.hr were 95% higher efficiency when three panels were put and hydraulic load 0,9 m3/m2.hr, while there was fluctuation with some of hydraulic load levels at turbidity level of 125 NTU and same number of panels.

The current study includes the effect of the type of porous medium on the heat transfer enhancement for double-pipe heat exchanger. Using the three types of the porous medium of balls (steel, ceramic and glass) with diameters (6.35, 6 and 7) mm respectively. The tests were carried out on a locally manufactured heat exchanger, consisting of a copper pipe with an inner diameter (20mm), an outer diameter (22mm) and a length of (1800mm), fixed inside a pipe made of galvanized iron with the same length of copper pipe with inner diameter (50mm) and thickness (5mm). The heat exchanger is insulated with a layer of glass wool to prevent leakage of heat to the area surrounding the exchanger. The tests carried out on the heat exchanger in four cases, the three cases for porous medium, also the case of exchanger without porous medium, and for all cases identical operating conditions, which is inlet temperature of hot, and cold water determined at (63 and 32)˚C and the number of Reynolds from (1100 to 9750) for cold water and (415 to 7500) for hot water. The experimental results showed that the highest thermal conductivity was obtained when the ceramic balls were used, which was estimated to be approximately (219.302) W/˚C and increased by (105.3%, 10.8%, 4.3%) for cases: without porous medium, glass balls and steel balls respectively. The effect of the pressure drop in the hot water side, was recorded the highest value for pressure drop when the ceramic balls were used and ranged from (0.5 to 19.5) mmHg and increased by (0.95%, 2.25%) when compared with the results of two cases for balls (steel and glass) respectively.