حسن عيسى داود

A nanofluid is a liquid that contains nanometer-sized particles. Nanofluids are obtained by dispersing nanometer-sized particles in conventional base fluids such as water, oil, ethylene glycol, etc. Nanoparticles of materials such as metallic oxides (Al2O3, CuO), nitride ceramics (AlN, SiN), carbide ceramics (SiC, TiC), metals (Cu, Ag, Au), semiconductors (TiO2, SiC), single, double or multi-walled carbon nanotubes, alloyed nanoparticles (Al70, Cu30), etc., were used to prepare the nanofluids. This paper presents a procedure for preparing Nanofluids, the properties of Nanofluids, and their applications in various fields, including energy, mechanics, and biomedicine. Then it defines the parameter that challenges the use of Nanofluids in different applications and finally suggests directions for future research on Nanofluids. The thermal conductivity of the Nanofluids is improved at a very low (< 0.1%) percentage of suspended particles. Nowadays, Nanofluids are used efficiently in non-traditional energy resources in absorbing solar energy to increase the temperature.

This study provides a detailed literature review on improving the thermal conductivity of nanofluids using multi-walled carbon nanotubes (MWCNTS). Numerous elements affect thermal conductivity, such as particle volume fraction, particle materials, particle shape, temperature, surfactants, ultrasonication time, and power. Studies have shown that these factors affect thermal conductivity, but the essential factor effect is dispersant (surfactant). Therefore, the existing problem that has not been addressed so far use a suitable dispersant that must not disintegrate at high temperatures and does not cause an increase in viscosity. These reasons caused problems in the equipment and made a non-homogeneous solution that decreased the thermal conductivity.

This study attempt to presents the heat transfer behavior of Al2O3 −water nanofluid in a coiled agitated vessel. The experimental work was conducted using 0.1%, 0.2%, 0.3% volume concentration of Al2O3-water nanofluids. The investigation was made by varying temperature from 30-80℃, and the speed of the propeller from 2 to 12 (rev per second) at three different flow rates of cooling water were 1.4, 1.8, 2.2, litter/min. The results exhibited significantly improved convective heat transfer using the nanofluids. The result was advanced for Nusselt number in terms of Reynolds number, Prandtl number, viscosity ratio, and volume concentration. The nanofluid heat transfer coefficient is organized to be higher in comparison with water and it is increasing with volume concentration increases. In addition; it is increased with increasing the propeller speed. Comparing the three different flow rates finds that the heat transfer coefficient is increased with decreasing flowrate within ±17.25 %.

Friction Stir Welding (FSW) used for welding similar and dissimilar materials especially to join sheet Al alloys. In this study, commercial pure aluminum and copper sheets (Al/Cu) with a thickness of 3mm were joined. We first preheated on the Cu side by pinless welding tool. Three different tool rotational speeds of 700, 1000 and 1500 rpm were used while the axial load and transverse speed were kept constant at 7.5 KN and 30 mm/min, respectively. We measured different parameters to determine the best rotational speeds for welding. Such as Field Emission Scanning Electron Microscopy (FESEM) and X-Ray Diffraction (XRD) analysis which showed that at 700 rpm there are three elements: Al, Cu and oxygen are present. While at 1500 rpm formation of different Intermetallic Compounds (IMCs). At 1000 rpm the interface has only Al and Cu in a uniform structure this result is due to the sufficient frictional heat generated at 1000 rpm and it considered perfect welds with acceptable mechanical properties.

After 10 vol. % SiC particles from the welding volume were inserted into the joint line, the mechanical properties of friction stir-welded joints were assessed. During the Friction Stir Welding (FSW) process, three different rotational speeds (1300, 1750, and 2000 rpm) were used. Field Emission Scanning Electron Microscopy (FESEM) was used to examine the microstructure across the Stir Zone (SZ), revealing a banded structure between the particle-rich and particle-free portions of the SiCp. When the joint was constructed at 1750 rpm, it displayed better mechanical properties. Because of the presence of SiCp, the Ultimate Tensile Strength (UTS) was enriched by 79.6% at 1750 rpm. Because of the pinning effect and larger nucleation sites caused by the SiC powder, this strength significantly increased. Furthermore, the hardened particle powder cracked the initial grains. When compared to the SiC-free sample, the SiC-rich sample had higher ductility at 1750 rpm. Finally, the fracture surface showed a good agreement with the equivalent ductility marks.