bahman rahmatinejad

In this research, the impact resistance behavior at low speed is analyzed for two types of common metal materials, steel and aluminum, and two types of epoxy composite materials reinforced with carbon fibers and glass, and the results related to the analyzes of metal and composite materials, including Von Mises stresses and strains, maximum shear stress and impact strain energy were compared in these materials. Based on the obtained results, steel with high Von Mises and shear stress and low Von Mises strain and shear strain had better performance than aluminum and composite materials. The steel sample bearing 23815 MPa had the highest von Mises stress and the composite sample reinforced with carbon fibers bearing 4763 MPa had the lowest von Mises stress. The highest Von Mises strain is in the carbon fiber composite sample compared to other metal and composite samples. This increase is about 870% more than the steel sample. This indicates the weakness of these materials in bearing shock loads. Also, the glass fiber reinforced composite sample has better performance compared to the carbon fiber reinforced epoxy composites. The reason for this is the better energy absorption properties of glass fibers compared to carbon fibers.

Valve originates from the French word, Soupape, meaning valve and its role is to control the mixture of air and fuel entering the engine and the exhaust fumes. In this research, dimensional defects and valve cracks were diagnosed with the help of machine vision and acoustic emission. After offline transfer of the images to MATLAB software, the images were processed and the dimensional parameters of the valve such as length, stem diameter, large diameter (seat) and valve stem curvature were measured. These parameters were compared with the actual sizes and the percentages of measurement error for these parameters which were estimated as 0.45%, 1.8% and 1.18%, respectively. Because there was no real way to measure the valve stem, the error percentage was not calculated for this parameter. To detect cracks from 60 similar new valves, an acoustic diagram prepared by AE-MAP 1.0 device and the acoustic diagram of 30 new and used valves were compared. The accuracy of the system in crack detection was estimated to be approximately 96.7%.

In this research, an experimental analysis of the effect of using aluminum oxide nanofluid (Al2O3) in improving the heat transfer of the engine radiator (XU7) with complete cooling system equipment was done. Tests in three pure water conditions; water and ethylene glycol (60:40) and finally with aluminum oxide nanofluid (Al2O3) with volume fractions of 1% and 2% and flow rates of 10, 21, and 32 liters per minute, in two slow and fast cycles. The cooling fan is done. The results showed that increasing the volume fraction of nanoparticles to the base fluid increases the heat transfer coefficient up to a flow rate of 21 liters per minute, and after that this coefficient decreases. By adding 2 percent by volume of nanoparticles to the base fluid at high fan speed, for flow rates of 10, 21, and 32 Lit/min, respectively, we see an approximate increase of 3%, 20%, and 16% in the displacement heat transfer coefficient compared to the base fluid. The pressure drop of the radiator with a volume fraction of 1 and 2% compared to the base fluid at a constant flow rate of 30 liters per minute was calculated as 22% and 40.8%, respectively.

Nanofluids, which are obtained from the distribution of nano-sized particles in normal fluids, are a new generation of fluids with great potential in industrial applications. The size of the particles used in nanofluids ranges from 1 nm to 100 nm. Viscosity is one of the important characteristics of nanofluids, which has a very important effect on heat transfer. In this research, the parameters affecting the viscosity of nanofluids were investigated. Different theoretical models can be used to estimate the viscosity of nanofluids. But the experimental results show that the viscosity of the nanofluid does not correspond well with the theoretical models. This difference is due to the effect of Brownian motion, the assumptions made when deriving the models, the mathematical modeling approach and the scattering techniques. In reality, the viscosity of nanofluid depends on many parameters such as base fluids, particle volume fraction, particle size, particle shape, temperature, shear rate, pH value, surfactants, dispersion techniques, particle size distribution and particle aggregation.

In this study, AL2O3+H2O nanofluid was used in a laboratory setting to test the thermal performance of the M13NI engine. AL2O3 nanoparticles were employed in this experiment along with base fluids made of water and ethylene glycol. We employed 20 nm nanoparticles with volume fractions of 1 to 2%. The outcomes demonstrated that the AL2O3 nanofluid made in the first 22 days was stable after being added SDBS sulphate. Additionally, the zeta potential, which was calculated to be 37.7 mv, shows the stability of the nanofluid. The heat transmission and pressure drop rose as the volume fraction of nanoparticles increased, while the merit parameter fell (ratio of heat transfer to pump power). At 1150 RPM and 1% volume fraction of nanoparticles in the water-based fluid, it was found that the heat dissipated increased by 7.2 and 13.1% in comparison to the mixture of water+ethylene glycol and pure water, respectively. When the volume proportion of nanoparticles in the base fluid increases, the radiator's outlet temperature decreases, resulting in a greater difference between the inlet and outlet temperatures and a faster rate of heat transfer. By utilizing nanofluid, it is possible to lower the radiator's size and the volume of the cooling system, so reducing the volume of circulating water and the engine's wasted power.

Nanoparticles are materials which have at least one of their dimensions (length, width, height) at the nano scale (among 1 and 100 nm). Nanofluids are obtained from the distribution of particles with nano dimensions in normal fluids. Common fluids such as water, oils and ethylene glycol, which are usually used in heat transfer, have limited ability in terms of thermal properties. The interesting properties of nanofluids (such as high heat transfer coefficient) and the great potential they show for increasing heat transfer have caused this group of fluids to be in the focus of researchers' attention in recent years. One of the key factors in optimizing the properties of these fluids is their stability. The gathering of particles and their agglomeration increases the possibility of sedimentation, reduces the stability of the suspension, and causes the loss of the properties of the suspension, such as thermal conductivity, viscosity, and increase in heat capacity. In this research, methods of increasing stability and inspection tools were investigated. The results showed that the simultaneous use of ultrasonic vibration and surface activating substances (surfactant) has a significant effect on the stability of nanofluid. And two methods of using DLS light scattering and ultraviolet-visible absorption spectrometry have been used by many researchers in their research in order to check stability.

In this study, the thermo-physical properties and thermal performance of Al2O3 nanoparticles were experimentally investigated in water-based fluid and ethylene glycol, and nanoparticles were produced by PNC1k-C device by electric explosion method. In order to measure the thermal conductivity, diameter and viscosity of the obtained nano-fluids, hot wire method (KD2-Pro device), dynamic light scattering (DLS) and Ostwald viscometer ASTM D445-06 were used respectively. The temperature range of the experiments was between 20 degrees to 50 degrees. The results showed that adding 1% by weight of sodium dodecyl gasoline sulfonate (SDBS) to Al2O3 + H2O stabilizes this nano-fluid for 22 days. In this case, the zeta potential is 37.7 mv, which indicates good nano-fluid stability. The results showed that with increasing the volume fraction of nanoparticles in the base fluid, the thermal conductivity, density, steam pressure and slope of the heating curve increase and the surface tension decreases. With increasing temperature, thermal conductivity and specific heat of water increased and density, viscosity and specific heat of nano-fluid decreased with different volume fractions. Also, with increasing the diameter of nanoparticles, the thermal conductivity decreased and the surface tension of the nano-fluid increased. The stronger the thermal properties of the base fluid, the greater the effect on the thermal conductivity of the nano-fluid. The obtained practical thermal conductivity coefficient was compared with the values of the prediction models of this coefficient. Based on the regression obtained for the calculated experimental results (R = 0.99), this value is consistent with the Timofeeva model.

The thermophysical properties and thermal performance of water- and ethylene-glycol-based nanofluids containing  and CuO nanoparticles were examined. Nanofluids were prepared at four concentrations (1- 4 vol%) using an electric mixer and magnetic stirrer, and the thermophysical properties were measured. Surfactants were used to improve stability. The transient hot-wire method (KD2-Pro device), Dynamic Light Scattering (DLS), and Ostwald viscometer (ASTM D445-06) were used to measure the resulting thermal conductivity coefficient, nanoparticle diameter, and nanofluid viscosity, respectively. The experiments were carried out in the 20 to 50 °C temperature range. Adding 1 wt% sodium dodecyl sulfate (SDS) to the CuO–water and the same amount of sodium dodecylbenzene sulfonate (SDBS) to the –water nanofluid were found to stabilize them for 20 and 22 days, respectively. Increasing the nanoparticle volume fraction, raising the temperature, and reducing nanoparticle diameter were found to increase the thermal conductivity coefficient. The density also increases with the nanoparticle volume fraction in the base fluid increasing. Moreover, at the same volume fraction, the CuO–water nanofluid had a higher density than –water. Better base fluid thermal properties amplify the effect on the nanofluid's thermal conductivity coefficient. The actual thermal conductivity coefficient was determined by comparing model predictions of the coefficient.

In this study, the thermal performance of a sample radiator under defined environmental conditions was studied. The relations governing the heat transfer for the air flow and the cooling fluid of water and ethylene glycol (50% -50%) were written in the radiator and then the characteristics of the radiator were changed and the relations re-examined. It was observed that the thermal performance of a radiator whose length was reduced by 25% but number of fins increased from 385 to 437 was equal to the thermal performance of the original radiator. The ϵ-NTU method was used to investigate this matter. Its optimal value was determined by the designed genetic algorithm 436. In addition, the distance between the two fins was reduced from 3.92 mm to 2.94 mm, the optimal value of which was determined by a genetic algorithm of 2.867 mm. Reducing the length of the radiator makes the radiator lighter and reduces construction costs, but reducing it too much can cause the cooling fans to come closer together and create a problem with heat dissipation.