Engineering and Technology Journal

The probable appearance of localized overheating (hot spot) represents one of the main matters for the reliability and safety of c-Si cells. It entails both a risk for the photovoltaic module's lifetime and a decrease in its operational efficiency. Partial shading is the most common cause of a hot spot in a PV system. The main aim of this work is to analyze the hotspot phenomena by I-V curve as well as IR thermography and investigate the impact of partial shading on the hottest cell experimentally to find its effect on the output power. The results show that at normal operating conditions (G=865W/m2 and Ta=39.7°C) the output power is 89.05W; the temperature difference between the hottest and cooled cell was about 6°C. Moreover, the short circuit current and consequently, the maximum output power reduced if only one cell fully or partially shaded. However, when the hottest cell is shaded by 25%, 50%, 75%, and 100% of the shaded area, the power losses were 37.17 %, 50.05%, 48.61%, and 52.86% respectively. Wheals, the hottest cell temperature was 80.6, 99.1, 101.4, and 62.4°C for 25, 50, 75, and 100% of the shading area, the major temperature difference observed at 75% of the shading area.

The purpose of this study is to study the ultrasonic peening influence upon the mechanical properties of the welded joints of 3 mm AA 7075-T73. Friction stir welding (FSW) was carried out by using milling machine and cylindrical tool with tapered pin. The used welding parameters were 710 rpm , 35 mm min for rotational and travel speed , respectively .Tensile tests results showed that the welding efficiency was about 60% for welded samples , and this value increased by using one and two lines ultrasonic peening treatment to 74% , and 71% , respectively , this improvement is due to generating compressive stresses along the surface of welded joints. The microhardness of the welded samples showed that there were fluctuations across the welded centerline and minimum hardness occur in the heat affected zone (HAZ).

Recently, composite materials were widely used in different applications due to their lightweight, and good thermal and mechanical properties. In this study, an attempt to manufacture laminate composites by hand layup was performed. Also, optimal parameters for the best surface roughness were investigated. Therefore, three parameters had been examined; spindle speed, feed rate, and depth of cut. The L9 Taguchi orthogonal array, signal to noise (S/N) ratio, and analysis of variance (ANOVA) were selected to determine the optimum parameters. To create composites, the compression method was employed. Four different types of composites were manufactured with 2.8 mm thickness, to determine the effect of the parameters on the surface roughness and for specified parameters using the CNC milling machine. The weight fraction ratio of fibers was 39%, the polymer was 34%, and 27% for Aluminum. The results showed that the optimum parameters for surface roughness in milling machine of composites for Polyester resin for aluminum–fiberglass composite are; spindle speed=5000 r.p.m, feed rate=1600 mm/min, depth of cut=1.6 mm and Ra=1.853 μm, and for epoxy resin; aluminum–carbon fiber composite is spindle speed=4000 r.p.m, feed rate=800 mm/min, depth of cut=1.2 mm and Ra=2.43 μm.

In this paper, experimental study on double pass solar air heater with wavy fins absorber has been investigated. The fins attached to the upper and lower surfaces of the absorber. Two wavy fins arrangement (3 and 7 fins) have been investigated with plan absorber by changing solar radiation intensity (500, 600, 700 and 800 W/m2), air mass flow rate form 0.008575 kg/s to 0.0214375 kg/s. The results of wavy finned absorbers are compared with plane and the improving in thermal efficiency reached 80% and 84% in 3 and 7 wavy fins absorbers respectively.

The non-conventional spinning process was adopted for producing polygons, but one of the process limitations is the error between design and the final product especially with no-mandrel. Dimensional accuracy was adopted for this purpose which gives an indicator of the ability of the formed part to matches the design and checking validated of the adopted methodology for producing rectangular cross-section spun parts, by comparing the coordinating points of real part with the points of the design model. The point of a real part was measured by using a sphere probe fixed on the three-axis milling machine and capturing the data of machine axis movements for the center location of the probe, also, the measurements oppositely took place, by offsetting the points of design along the normal vector for comparison with the real part points. Three parameters were invested for study the effects on the dimensional accuracy, these parameters are spindle speed (48, 68, and 135 RPM), feed ratio (0.16, 0.22, and 0.32 mm/rev), and the ball diameter of the forming tool (16, 22 and 25 mm). The results show that tool ball diameter mainly affecting dimensional accuracy with a higher value of average error reach (6.47mm) when 16mm diameter of tool ball was used, on the other hand, the minimum average error was 1.705mm at low spindle speed.

The dynamic effects in the “upper“ drum of the boiler (mechanical’s effects) are very complex problems and critical due to the pressure disturbance in the upper drum of the boiler. This work deals with an experimental investigation of the dynamic behavior of the boiler drum level system is reported from plant data (Al-Quds power plant) in Baghdad / Iraq under a particular condition of operating, and the mathematical equations of the boiler model variables explained and defined. The dynamic effects are investigated with increasing steam mass flow rate (10% and 20%) at the outlet of the boiler. The results showed that the rapid rise in the rate of steam mass flow causes the dynamic effects to increase (shrink and swell) by 15%, rates of evaporation and thus causes an increase in the volume of water inside the upper drum boiler that causes overheating in the tubes.

The goal of the present work is to study the effect of different sintering temperatures (900, 1000 and 1100 ) on fatigue and mechanical characteristics of the metal matrix AA5052 reinforced with 5% of TiO₂ nanoparticles. The stir casting process is used for manufacturing of AA5052/TiO₂ nanocomposite. The mechanical characteristics of nano composites have been obtained at ambient temperature. The results of mechanical properties showed that the best enhancement in hardness (HB), ultimate tensile strength (UTS) and yield strength (YS) is occurred in nanocomposite with 1000  sintering temperature (ST). However, the fatigue test results showed that the samples manufactured under 1000  (ST) have longer fatigue life compared to other materials with different sintering temperatures. The endurance fatigue strength is improved by 7.2% compared to metal matrix. The experimental results showed that the microstructure image of 1000  (ST) composite has uniformly distributed of TiO₂ in AA5052 matrix.

Human actions such as electricity generation are contributory causes of climate change. In a quest to reduce the emission of greenhouse gases associated with electricity generation from fossil fuels, the world is turning to renewables. Renewable sources, however, also do have an impact on the environment. Likewise, renewable electricity generation is also dependent on the climate. Hydro, Wind, and Solar are the popular renewable energy sources for the generation of electricity. This work reviews the impact of these renewables in electricity generation on the environment. It also considers the effect of climate change on its use. The construction of renewable electricity generating plants leads to habitat disruptions and can also cause fatalities. Climate change weighs an enormous impact on the performance of renewable electricity generating plants. The recent blackout experienced in Texas as a result of the cold weather is a good example. The end of extreme weather conditions is not yet, and the need to start preparing to prevent a blackout re-occurrence. A possible solution for sustainable renewable electricity generation in extreme weather conditions lies in synthetic fuel availability.

In this research, a practical study and appraisal of the thermal performance for the solar collector with vacuum tube has conducted Two types of nanomaterials (aluminum and aluminum oxide) have added to distilled water with nanoparticles diameters of 30 nm and 50 nm respectively. The nanomaterials were used in three several concentrations and three several flow rates which used as a working fluid in evacuated tube solar collector (ETSC) in order to increase the efficiency and beneficial thermal gain. An electronic double-sided reflective and absorbent electronic curtain were added to enhance the performance and control the temperature of the nanoscale. A clear improvement in efficiency was observed when using the reflective curtain that helped to speed up the Nano fluid heating and controlling the required temperature.

Porous media and solvent CO₂ at supercritical pressure were investigated experimentally to study the effect of convection heat transfer in vertical mini-tubes. Mini-tubes diameter (5 and 8 mm) with medium porosity of 0.5 are proposed in experimental investigation. Experimental conditions consisted of bulk fluid, wall temperatures ranged from 33 to 55 oC, and 8 to 10 MPa of pressure. Reynolds number, Mass flow rate, and heat flux were 1750 to 21000, 0.5 to 4.5 Kg/h, and 3.25×104 to 1.1×105 W/m2 respectively. Some chemical additives like Ethanol, Chloroform, Acetone, Dimethyl sulfoxide, and Methanol were considered. A special focus was dedicated to studying the influence of heat flux, inlet temperature, and mass flow rate at measured values of wall and fluid bulk temperatures, and coefficients of local heat transfer for mini-tubes and porous media. A higher effect was noticed on the convection heat transfer by buoyancy and properties of the thermophysical variable of solvent CO2 in mini-tube at vertical position. However, when these results were compared with the controls (empty tube) shoewn dramatically different results. Heat transfer coefficient was bigger about 4 times when using the porous media tube compared with the empty type in the case of using a 5% of acetone solvent.

The object identification properties with tactile sensing are valuable in  interaction with the environment for both humans and robots, and it is the core of sensing used for exploration and determining properties of objects that are inaccessible from visual perception. Object identification often involves with rigid mechanical grippers, tactile information and intelligent algorithms. This paper proposes a methodology for feature extraction techniques and discriminates objects for different softness using adaptive robotic grippers, which are equipped with force and angle sensors in each four fingers of an underactuated robot hand. Arduino microcontroller and the Matlab program are integrated to acquire sensor data and to control the gripping action. The neural-network method used as an intelligent classifier to distinguish between different object softness by using feature vector acquired from the force sensor measurements and actuator positions in time series response during the grasping process using only a single closure grasping. The proposed method efficiency was validated using experimental paradigms that involving three sets of model objects and everyday life objects with various shapes, stiffness, and sizes.

In this work, the structure of the linear elevator prototype had been investigated numerically using finite element method. The linear motor structure parameters analyzed using Maxwell ANSYS. The time-stepping method depending on Maxwell equations be applied for analyzing and optimizing the magnetic and force characteristics. While the elevator structure parameters were analyzed using ANSYS workbench based on the principle of virtual work. The frame considered as clamped- clamped beam, and the base of the car considered as thin plate with small deflection. The analysis done with maximum applied load of 360 N at 1.5 safety factor. The results show the distribution of the magnetic lines, the flux density values plus the leakage flux inside the slots. The maximum Von-Mises stress and the deformations of the frame and plate at maximum load are acceptable and present save design. In which the maximum deflection of the thin plate not exceed (thickness/5) at maximum design load.  

In this research, an ejector was designed and manufactured from brass metal as part of a cooling system to cool agricultural products, work of ejector is based on the Venturi principle. The primary fluid is air and steam of product is the secondary fluid, used the primary pressure (1, 8, 1) bar for the purpose of conducting the experiment. The ejector was manufactured from a number of interconnected parts to give the final shape. The performance of the ejector was analyzed theoretically, through operating of system evaporation of water take place in vessel  leads to cooling product at change operation condition and the examination, it was reached:
a- The cooling efficiency of the product increases by increasing the primary pressure.
b- The cooling efficiency of the product increases by decreasing the mass of the product.
c- The loss weight of the product increases by increasing the primary pressure.

Photovoltaic (PV) panels produce electrical energy comparable to the cumulative amount of PV radiation generated on surface of sun. The solar modules influence on temperature of PV panel and for work with its standard specifications in Iraqi environment can be used nanofluid for cooling PV and improve performance. The developed thermal model for proposed cooling method has shown on the way to be an efficient design tool that can help engineers to reduce the time and cost of experimental testing. The improvement in temperature reduction using direct flow technique at rear sides of PV panel achieved electrical and thermal performance enhancement. The enhancement of overall efficiency at 1 g of nanofluid  is  showed  15%  but in 1.5g  nanofluid is  18%. As well as the enhancement of thermal efficiency at 1 g and1.5g of nanofluid are showed 19% and 27% respectively. So in Electrical efficiency at 1 g of nanofluid is showed 11% and in 1.5g  nanofluid is  14%.The experimental results have shown that the utilization of nanofluid (Al2O3) as a result of its high thermal conductivity and tiny particle size. The coefficient of heat transfer and Nusselt number increasing with the increase of concentration of nanofluid, It can be concluded that has great impact, especially in Iraq condition where the temperature is normally high and can improve their performance and efficiency by adding nanofluid for cooling system.

Gas turbines are engines an energy plant makes use of for generating the rotary motion to show power generators. The gas turbine is largely a combustion engine for changing natural gas or different liquid fuels to rotational mechanical energy. Often, the gas turbine generates excessive noise or vibrations. In this work, the problem of vibrations occurrence in the gas turbine model MS9001E used in the south Baghdad power station is solved. This is done by making a groove in the bearing pad to increase the oil flow, replacing the bearing type with a tilt-pad bearing type with damper. The finite element method was used in the analysis process by ANSYS program. The results showed a decrease in the values of vibration amplitude, total deformation, stress, and strain.