Sharif Digital Repository

Hydrothermal synthesis of CuO nanoparticles under near-critical and supercritical conditions was investigated from two different standpoints in the current study. The first standpoint was optimization of "yield", "purity", and "size of the nanoparticles" that were optimized at T = 500 °C, time = 2 h, [Cu(NO3)2] = 0.1 mol dm-3, and pH 3. This was achieved by undertaking an orthogonal experiment design methodology and performing different instrumental analyses, such as X-ray diffractometry, inductively coupled plasma spectrometry, and transmission electron microscopy, along with treatment of the data by analysis of variance (ANOVA). The second goal of the study was elucidation of the... 

A large variety of modifications have been presented for the temperature dependent function (α) existing in the attractive term of cubic equations of state (CEOS). Most of α-functions attempted to modify the vapor pressure prediction of polar components while other modifications have focused on both polar and non-polar compounds and other relations have considered an expansion of polynomials in the acentric factor (ω) and reduced temperature (Tr) to predict vapor pressure more accurately. In most cases such as Soave and Peng-Robinson equations of state, the suggested α-functions do not show a limiting behavior when temperature increases infinitely. In addition, the incompetency of many... 

Shock control bump (SCB), suction and blowing are three flow control methods used to control the shock wave/boundary layer interaction to reduce the resulting wave drag in transonic flows. An SCB uses a small local surface deformation to reduce the shock wave strength, while the suction decreases the boundary layer thickness and the blowing delays the flow separation. Here, we will use a multi-point continuous adjoint optimisation scheme to find the optimum design of suction and blowing separately or together, or with the SCB, on two supercritical airfoils, i.e. RAE-5225 and RAE-2822, for a wide range of off-design transonic Mach numbers. The RANS flow equations are solved using the Roe’s... 

Both shock control bump (SCB) and suction and blowing are flow control methods used to control the shock wave/boundary layer interaction (SWBLI) in order to reduce the resulting wave drag in transonic flows. A SCB uses a small local surface deformation to reduce the shock-wave strength, while suction decreases the boundary-layer thickness and blowing delays the flow separation. Here a multi-point optimization method under a constant-lift-coefficient constraint is used to find the optimum design of SCB and suction and blowing. These flow control methods are used separately or together on a RAE-2822 supercritical airfoil for a wide range of off-design transonic Mach numbers. The RANS flow... 

Carbon-doped zinc oxide/reduced graphene oxide (C-ZnO/rGO) was prepared by a facile one-pot supercritical methanol method. The synthesized C-ZnO/rGO nanocomposite with flower-like ZnO micro-rods (MRs) synergistically inherited all the advantages of carbon doping and rGO heterojunction and exhibited high photocatalytic activity for the photodegradation of methyl orange (MO) under visible light. The x-ray diffraction (XRD) results indicated that in presence of GO, a new carbon-doped phase was formed at the high temperature and pressure of supercritical methanol. The x-ray photoelectron spectroscopy (XPS) at low binding energies demonstrated that the valence band of C-ZnO-rGO is up-shifted by... 

Supercritical water reactor is one of the generation IV reactors which is basically a creative mixture of conventional PWRs and supercritical pressure steam boilers. Application of nanoparticles provides an effective way of improving heat transfer characteristics of conventional coolants; thus, utilization of a nanofluid coolant in the conceptual design of this reactors is quite reasonable and inevitable. Reactor coolant at supercritical pressure dose not experience any phase change and is heated up to 500 °C in three pass core design. In this paper, thermal–hydraulic analysis of applying a water base Al2O3 nanofluid with different nanoparticle mass fractions were investigated using a porous... 

In this study, the effect of moving pressure source and channel parameters on the generated waves in a channel was numerically investigated; draught, angle of attack, and profile shape as parameters of pressure source, and water depth and blockage factor as channel parameters for wave height. Firstly, the chosen Computational Fluid Dynamics (CFD) approach was validated with the experimental data over a range of speeds. Then, the CFD study was conducted for further investigations. It was shown that that by enlarging draught, angle of attack, and beam of the pressure source, the wave height generated would be increased. Channel study showed that it was possible to increase the wave height... 

To study the gas injection scenario for successful implementation of enhanced oil recovery (EOR)processes, the prediction of interfacial tension (IFT)between injected gas and the crude oil is of paramount significance. In the present study, some intelligent methods were developed for determining IFT values between supercritical CO2 and normal alkanes. IFT was considered as a function of temperature, pressure, and molecular weight of normal alkanes. The developed methods were Multilayer perceptron (MLP), Genetic Algorithm Radial Basis Function (GA-RBF), and Conjugate Hybrid-PSO ANFIS (CHPSO-ANFIS). The average absolute percent relative errors (AAREs)for the stated techniques were found to be... 

Characterization of the transcritical coaxial injectors, accounting for the geometrical features and thermodynamics nonlinearities, is of both practical and fundamental importance. In the present study, the interactions and effects of turbulent mixing and pseudo-boiling phenomena are investigated. To do this, the mixing dynamics of bi-shear jets injected under trans- and supercritical conditions has been investigated numerically using the large-eddy simulation technique. The numerical framework provides real-gas thermodynamics and transport properties, using the Peng-Robinson equation-of-state and Chung's models, respectively. The obtained flow quantities are in good agreement with the... 

The interactions and effects of turbulent mixing, pseudo-boiling phenomena, and chemical reaction heat release on the combustion of cryogenic liquid oxygen and gaseous hydrogen under supercritical pressure conditions are investigated using RANS simulations. Comparisons of the present numerical simulation results with available experimental data reveal a reasonably good prediction of a supercritical axial shear hydrogen-oxygen flame using the standard k-ε turbulence model and the eddy dissipation concept combustion model with a 23 reaction steps kinetics for H2-O2 reaction. The present simulation qualitatively reproduced oxygen injection and its reaction with the co-flowing hydrogen, which is... 

Recently, hybrid graphene–quantum dot systems have attracted increasing attention for the next-generation optoelectronic devices such as ultrafast photo-detectors and solar energy harvesting. In this paper, a novel, one-step, reproducible, and solution-processed method is introduced to prepare hybrid graphene–PbS colloids by employing supercritical ethanol. In the hybrid nanocomposite, PbS quantum dots (~3 nm) are decorated on the reduced graphene oxide (rGO) nanosheets (~1 nm thickness and less than 1 micron lengths). By employing X-ray photoelectron and Raman and infrared spectroscopy techniques, it is shown that the rGO nanosheets are bonded to PbS nanocrystals through carboxylic bonds.... 

A single step supercritical method was introduced for synthesis of “magnetite - reduced graphene oxide (M-rGO)” composite in supercritical methanol. Modified surface, smaller size, lesser cytotoxicity, and homogenous dispersion of Fe3O4 nanoparticles on the graphene surface were advantages of this new M-rGO composite in comparison to the materials synthesized by conventional wet chemical method (M-GO). Nanocomposites were injected in tissue equivalent phantoms of agarose gel in 10 mg/g dosage, and were irradiated by a 1600 mW laser beam at wavelength of 800–810 nm. The M-rGO and M-GO were found to be the most and the least efficient samples for increasing the temperature of the phantom. As... 

Infection is a disease that is mainly caused by different Gram-negative and Gram-positive bacteria. Treatment of infections requires a considerable amount of antibiotics, which can cause serious damage to the patient's body. Delivering the antibiotic only to the site of infection can prevent these destructive effects, such as the destruction of the normal intestinal flora. The drug delivery system through carriers will take antibiotics into a part of the body involved in the disease. Niosome nanoparticles, which have been made from non-ionic surfactants, have been emerging as ideal drug/antibiotics delivery vehicles. Recently, niosome formulations have been targeted to reduce toxicity and...