فهرست مطالب younes bakhshan

The present study examined the pool boiling process in a specific geometry by designing, constructing a laboratory complex and Providing Empirical Relations. Investigation of pool boiling process, electrical resistance, critical heat flux, heat transfer coefficient, bubble growth and departure, bubble growth frequency, and nucleation site density by applying heat flux to critical heat flux was carried out on wire mesh element in deionized water at different temperatures. According to the results, increasing the size of mesh and fluid temperature decreased the critical heat flux. In the case of a wire mesh with a constant size of mesh, a fluid with a constant temperature, and the use of heat flux values less than the critical heat flux, the wire temperature increased, but it decreased in the case of increasing the size of mesh, a fluid with a constant temperature and applying critical heat flux values. In the case of a constant size of mesh, the heat transfer coefficient was constant by increasing fluid temperature at values of heat flux less than the critical heat flux, but the heat transfer coefficient was increased with increasing values of heat flux less than the critical heat flux and decreased at critical heat flux values. By increasing 4 times the mesh size in the fluid at 30, 70 and 100°C in the critical heat flux, the heat transfer coefficient decreases by 0.7%. The maximum bubble growth frequency is related to the 0.5 mm wire mesh in 100°C fluid with 0.0763 bubbles per millisecond.

Today, the application of supercritical fluid extraction (SFE) has been the focus of many researchers in various industries due to suitable operating conditions, environmental friendliness (no use of organic solvents) and high efficiency. In this process, a solvent is used for separation in supercritical conditions. Pharmaceutical, oil extraction, and oil and gas industries have conducted extensive research in this field. Electronic and electric devices are constantly being upgraded and updated due to the rapid advancement of science and technology, which creates a number of issues with handling electric and electronic waste (e-waste). The most significant issue is that it is challenging to safely dispose of halogen flame retardants and refractory polymers in e-waste. Supercritical fluid (SCF) techniques provide significant environmental benefits over previous disposal methods like pyrolysis and acid leaching since they pose no dangers for air or water contamination. This study discusses and provides a summary of the basic concepts and appropriate factors of supercritical fluid extraction (SFE). SCF methods were claimed to have recovered precious metals, base metals, and other inorganic minerals from e-waste with a recovery efficiency of further 93%. This study reviews the recent advances in supercritical water (SCW) and supercritical carbon dioxide (SCCO2) extraction technologies for metal recovery from e-wastes. On the other hand, hybrid technologies are significantly improving in this field which could be considered for future studies.

The present study examined the pool boiling process in a specific geometry by designing and constructing a laboratory complex. Investigation of pool boiling process, electrical resistance, critical heat flux, heat transfer coefficient, bubble growth and departure, bubble growth frequency, and nucleation site density by applying heat flux to critical heat flux was carried out on a ring wire in deionized water at different temperatures. According to the results, increasing the number of rings and fluid temperature decreased the critical heat flux. In the case of a ring wire with a constant number of rings, a fluid with a constant temperature, and the use of heat flux values less than the critical heat flux, the wire temperature increased, but it decreased in the case of increasing the number of rings, a fluid with a constant temperature and applying critical heat flux values. In a ring wire with a constant number of rings, the heat transfer coefficient was constant by increasing fluid temperature at values of heat flux less than the critical heat flux, but the heat transfer coefficient decreased at critical heat flux values. The diameters of the produced bubbles were enhanced by increasing heat flux and they separated from the rings when combined. At the beginning of the reddening of the ring wire, a critical heat flux occurred, and considering 110% of the time required for the critical heat flux, the images of the state of the ring wire after the critical heat flux are presented.

To predict static aeroelastic behavior accurately, two-way fluid and structure interaction (FSI) coupling methods are used to calculate the static deformations and aerodynamic characteristics of the deformed rocket. According to the studies, little research has been done on the weight reduction of space structures. Therefore, due to the stratigicness of the Fin of space structures, the mechanical behavior of the sheets for the construction of the Fin has been experimentally studied using a constrained groove pressing (CGP) method and a comparison has been done between the amounts of deviation caused for a rocket flying in different Mach numbers and different angles of attack, by simulating a two-way FSI Method for WAF and Flat Fins models with two types of material, the CGP 7075-T6 aluminum, and the 4130 steel. Results of constrained groove pressing show that with the increase in the steps of this process, 7075-T6 aluminum with 38% increase of yield strength in fourth transit, 34% increase in tensile strength, 40 percent decrease in elongation, and 62% increase in toughness relative to the prototype, will be produced. The total deviation in WAF Fin is much less than the flat Fin. Also, deviations of Fin made of CGP 7075-T6 aluminum is less than the Fin made of 4130 steel.

In this research blood as a fluid with both Newtonian and non Newtonian viscosity with different volume fraction of nano particle in a 3D microchannel which is revolving around vertical direction with Electricity flow applies on Tow parallel faces Perpendicular to X axis. In different Nano particle volume fractions with Newtonian and non-newtonian viscosity result are obtained and results for velocity are showed numerical Results were determined that velocity of fluid is increased with increasing in volume fraction and The changes in the non-Newtonian fluid velocity are much lower than Newtonian fluids .In fact, the flow of non-Newtonian fluids requires a stronger electrical field.

In this paper, non-equilibrium molecular dynamic simulation has been employed to study the effect of wall interfacial properties and temperature of system on the hydrodynamics and heat transfer of water molecules in a nanochannel. The charges and Lennard-Jones potential are used to modeling the interactions between particles. The external forces are applied to the mass center of every water molecule in the x direction to create its flow and the thermal and hydrodynamics behavior of the water molecules was then analyzed. To construct the wall pore model, two silicon solid surfaces were used and the temperature of system has been controlled by utilizing Nose-Hoover thermostat. The interaction strength 〖(ε〗_(Si-W)) between wall atoms and water's oxegen atoms were adjusted to indicate different surface wettability or wall–fluid interaction. The higher value of 〖(ε〗_(Si-W)), causes the higher hydrophilic wall interface. The simulation results showed that the interaction strength, (ε_(Si-W)) and temperature of system is important in determining the nanorheology of the nanochannel and flow resistance of the confined water. The drag resistance at the solid–fluid interface will increase with increasing the hydrophilicity of walls 〖(ε〗_(Si-W)). Also the heat dissipation of system will increase, with increasing the drag resistance at the solid–fluid interface, and it results, the heat flux of system will decrease.

In the present study, a molecular based scheme has been developed for simulating of surface roughness and cavitation effects on nano- scale flows. In the nano-channel flows, there are some differences on the flow friction between roughness and cavitations which are not well studied. In the presented approach, based on the Molecular Dynamics Simulation (MD), the Lennard-Jones potential is used to modeling the interactions between particles. Each atom of the solid wall is anchored at its lattice site by a harmonic restoring force and its temperature has been controlled by utilizing thermostat.The roughness and cavitation have been implemented on the lower side of channel. To make a comparison between the effect of roughness and cavitation, the same dimension is used for both of them. Obtained results show, those hydrodynamic characteristics of flow and the walls shear stress depends on the roughness and cavitation sizes. The roughness on the bottom wall has more effect than cavity wall on the velocity and density profiles. Also results show that the presence of roughness on the bottom wall respectively increases the shear stress on the bottom wall and decreases its value on the top wall while, the presence of cavitation on the bottom wall has no effect on the top wall and just increase the bottom wall shear stress.