Iraqi journal of mechanical and material engineering

The aim of this research is to study the mechanical properties and wear behavior of aluminum composite material (AMCs) reinforced with silicon carbide particles with varying percentages (0, 3, 6 and 9) wt. %. These composites samples were prepared by stir casting process. Tensile strength, compression strength, hardness and wear resistance of the prepared composites were analyzed. The result showed that adding SiC reinforced in Al matrix increased tensile strength, compression strength, wear resistance and hardness with increased wt. percentage of silicon carbide reinforced AMCs. Maximum tensile and compression strength and hardness showed at 9 wt. percentage SiC reinforced AMCs.

In the current work, a thermosyphon was used to investigate the effect of condenser length on its performance. Experimentally by using a pipe of copper having same evaporator length of 120 mm and three different condenser lengths which were 400 mm , 500 mm and 600 mm. The internal and external diameters of the thermosyphon were 26 mm and 28 mm respectively. The evaporator part of the thermosyphon was immersed in the electrical transformer oil, which heated by external heater from ambient temperature to approximately 80 oC, while the condenser part was left to cool naturally by air. Five thermocouples were located on the thermosyphon wall to read the temperature distribution at different positions. The working fluid was water with filling ratio of 50%.
The results have obviously shown that temperature gradient was decreased when the condenser length increased and giving a better performance for heat dissipation. The percentage of temperature gradient was positively correlated to the condenser length and it was found that condenser length of ( 400 , 500 , 600) mm gave percentage of decreasing temperature gradient are 67.94 % , 72.94 % , and 77.06 % respectively with respect to that without using thermosyphon .

In this work, surfaces of Al 6061 alloy were coated using anodizing and micro–arc oxidation ( MAO) duplex processes. MAO electrolyte was modified using ( 2-6 g/l )Al2O3 additives . X-ray diffraction (XRD), scanning electron microscopy (SEM), Vickers indenter, atomic force microscopy (AFM), and Microprocessor coating thickness meter ,were employed for characterization of the deposited coatings .Results showed that the coatings contained porous oxide γ-alumina with morphologies characterized by different levels of porosity non-uniform distribution, and their thickness and hardness increased by the increasing of Al2O3 additives. The research demonstrates that a relatively hard (421-490Hv), thick (43-65μm) and uniform coatings, can successfully be deposited on preanodized Al alloy (12-15 μm with hardness of 190Hv) using Al2O3 additives containing MAO electrolytes as a new method for more future research on surface improvements of Al alloys.

In this study, the stability of a simply supported pipeline conveying fluid with different velocities and resting on viscoelastic foundation is investigated by using finite element analysis, and the critical fluid velocity with different parameters such as stiffness and viscous coefficients of foundation are obtained. This structural system could be found in pipes conveying petrol, water, and sewage. The foundation is simulated using the modified Winkler\'s model to introduce the effect of time dependent viscosity term. Some known results are confirmed and some new ones obtained. Two components of foundation, stiffness and viscosity, seemed to act on the critical flow velocity of the pipe in contrary trend. Where, increasing the foundation stiffness tended to increase the critical flow velocity in the pipe. While, increasing foundation viscosity attempted to decrease it. At some ranges of pipe length, the foundation viscosity effect seems to be more extreme. Increasing the fluid velocity leads to monotonic reduction in the system damping ratio. Two parameters, pipe length and fluid density which relate to the natural frequency of pipeline conveying fluid are studied in detail and the results indicate that the effect of Coriolis force on natural frequency is become more effective by increasing pipe length and fluid density besides increasing fluid flow velocity.

Thermal systems are involve in many applications the most important of which are cooling system, so most research aims to improve heat transfer, the enhancement of egg shell nanoparticles with distilled water in double pipe counter flow heat exchanger was studied. The results show that Nusselt number increase as volume concentration and Reynolds number increase. The increasing percentage of Nusselt number, friction factor, performance factor of (10.95, 11.878 and 6.88)% respectively than plain tube for maximum volume concentration and volume flow rate 5%,1.6 l/min respectively, fully developed turbulent flow, homogeneous Nano fluid with ranging Reynolds number from 3256.27 to 5202.33. ANSYS FLUENT 2015 package is used to simulate the heat transfer and fluid flow in the heat exchanger. The results show that the heat transfer increases when Nano fluid was added. The agreement observed with the experimental work with maximum discrepancy (12%).

A humidification-dehumidification (HDH) desalination system integrated with flat plate collector (FPC) was investigated experimentally in an attempt to study the production of fresh water using renewable energy. Two types of solar collectors; concentrated parabolic trough solar collector (to heat oil) and non-concentrated (FPC) (to heat saline water before entering the humidifier) were used in this work. Photovoltaic panels (PV) with DC to AC inverter are used to operate, air fan, oil pump and water pumps. The experiments were carried out in August 2016 under climatological conditions of Baghdad- Iraq (latitude 33.33° N, of longitude 44.4° E). Performance of the HDH system is examined with and without FPC. Saline water was first filtered by a sand filter to reduce water turbidity by (85% – 90%) and is also working to eliminate lichens and the suspended solids from saline water. This filtered saline water was processed through humidification dehumidification system based on solar collector for heat source. Selected water samples are tested for Total Dissolved Salt (TDS) in (mg/l), pH, turbidity in (NTU) and electrical conductivity in (μs/cm) measured before and after desalination process. Before filter the water Turbidity is about (11.2 NTU) while after sand filter it is decreased to (1.94 NTU) and it was (0.1 NTU) after dehumidifier. Results showed that the accumulated productivity is (1050 milliliter); it has been improved by 62%when using FPC.