Sharif Digital Repository

Poly(vinyl alcohol)-polyethylene glycol, PVA-PEG, blended membrane were prepared using supercritical fluid assisted phase-inversion method, in which scCO2 was used as the anti-solvent. Poly(vinyl alcohol) was utilized as the main polymer, polyethylene glycol as the additive, and dimethyl sulfoxide (DMSO) as the solvent of these polymers. Taguchi method was used to investigate the effect of some operating parameters on the morphology of the membranes. The L16 orthogonal array was selected under the following conditions: pressure (100, 135, 165 and 200 bar), temperature (40, 45, 50 and 55°C) and PEG weight percent (0, 0.33, 0.66, and 1%). Total polymer concentration of solutions in all... 

Vapor liquid equilibrium (VLE) data has significant role in designing processes which include vapor and liquid in equilibrium. Since it is impractical to measure equilibrium data at any desired temperature and pressure, particularly near critical region, thermodynamic models based on equation of state (EOS) are usually used for VLE estimating. In recent years due to the development of numerical tools like artificial intelligence methods, VLE prediction has been find new alternatives. In the present study a novel method called Least-Squares Support Vector Machine (LSSVM) used for predicting bubble/dew point pressures of binary mixtures containing carbon dioxide (CO 2) + cyclic compounds as... 

Various models have been applied composed of the Peng-Robinson equation of state (PR-EoS) and the Soave-Redlich-Kwong equation of state (SRK-EoS) associated with three mixing rules including the following: Wong-Sandler (WS), van der Waals one (vdW1), and van der Waals two (vdW2) for phase behavior modeling of mixtures of supercritical CO2+different ionic liquids in vapor-liquid equilibrium (VLE) region. It has been found that the PR EoS implying the WS mixing rule can be used as a reliable thermodynamic model to perform a thermodynamic consistency test on the experimental data of phase behaviors of the supercritical CO2+ionic liquid systems (19 commonly-used ionic liquids have been studied).... 

A molecular dynamics (MD) simulation is employed to study the phase transition process in argon induced by shock wave transmission. Deriving the relation between the shock and piston velocities, the theoretical equation of state for argon is presented. Also, argon equation of state is obtained by measuring the quantities directly from simulations to be able to detect the phase transitions. The phase transition is also detected by using argon phase diagram and free energy calculations. A comparison shows good agreement between the theoretical and MD results for the phase transitions. Based on these simulations, it is concluded that under a shock wave transmission with suitable energy, the... 

A new simple and explicit reduced temperature and reduced pressure function has been proposed in the present study for modifying Redlich-Kwong equation of state (EoS) to calculate the density of carbon dioxide in the supercritical region. The average absolute error of the model was found to be 1.63 and 2.07% in the comparison with the literature and NIST density data respectively, which demonstrates superiority of the model over other EoSs  

The effective parameters such as particle size, temperature, pressure and extraction time on supercritical carbon dioxide extraction of cocoa butter form cocoa seed were studied in order to find the optimum conditions for extraction. Particle size from whole cocoa nibs to one millimeter diameter, extraction temperature from 35°C to 55°C, extraction time from 2 to 8 hours and extraction pressure from 5 to 20 MPa were investigated and optimized. The optimum results (according to the limitation of the apparatus) of 5.2% extraction efficiency, suggests that pure CO2 is not a suitable solvent for extraction of cocoa butter in the investigated range of parameters and therefore the use of a... 

A new flow model of high performance light water reactor (HPLWR) is discussed in the present study. HPLWR involves a negative density reactivity coefficient with high time delay. This factor decreases the stability of such reactors when transient and abnormal accidents happen. A new design for enhancing safety and efficiency in such reactors is presented. In the new design, the fluid passing through the moderator channels and the assembly gaps (known as a moderator) flows in channels detached from coolants. It is possible to control the moderator mass flux. Increasing or decreasing the moderator mass flux will modify the moderation capacity, which results in a change in the reactor power.... 

The High-Performance Light Water Reactor (HPLWR) is the European version of the Supercritical-pressure Water Cooled Reactor (SCWR). Light water reactors at supercritical pressure, being currently under design, are the new generation of nuclear reactors. The present article is a thermal-hydraulic analysis of the HPLWR fuel assembly cluster. The existing thermal hydraulic codes are not capable of analyzing and designing the HPLWR fuel assembly. It is necessary to introduce a new thermal-hydraulic code that can incorporate the parameters and specifications of the HPLWR fuel assembly. The governing equations include energy, mass and momentum equations beside thermal-hydraulic equations are... 

Both the equation of state-excess Gibbs energy (EoS/GE) model and the cubic plus association (CPA) equation of state (EoS) are compared in this study with respect to their accuracy in the correlation of PVTx for systems such as water/methanol, water/ethanol, water/benzene, water/toluene, water/methane, water/n-butane, water/n-pentane, water/n-hexane, water/heptane, and water/octane, in supercritical conditions within temperature and pressure ranges of (573-698 K) and (7. 0-276. 0 MPa), respectively. In the proposed EoS/GE model, Peng-Robinson (PR) equation of state, linear combination Vidal-Michelsen (LCVM) and Wong-Sandler (WS) mixing rules in conjunction with UNIQUAC activity coefficient... 

In the present study the neutronic analysis of fuel assembly cluster of the HPLWR is discussed. Neutronic calculations are performed using WIMS-D4 and CITATION codes. Thermal-hydraulic code containing the properties and specifications of the fuel assembly of HPLWR is utilized. The calculated axial power in each selected control volume is used in the thermal-hydraulic code to get the properties of the fluid and fuel needed for further neutronic analysis. The process of coupling continues until convergence is achieved. Finally, the obtained neutronic results including axial power distribution, neutron flux, and power peaking factors are discussed in the present article  

The current study is aimed at comparison of adsorption behaviors of silica-supported Cu nanoparticles (Si-N-Cu) and micrometric copper powder (Mi-Cu) for uptake of iodine vapor. The Si-N-Cu was synthesized by the decomposition of aqueous Cu(NO3)2 solution at supercritical condition, followed by reduction of the sample by H 2-N2 mixture. The Si-N-Cu sample with 29.4 nm Cu particles adsorbed 95% of I2 at partial pressure 10-5 bar in 1 h, while the 1 μm Mi-Cu adsorbed 51% of iodine in 6 h, indicating higher yield and faster kinetics of the nanometric sample. Theoretical analysis revealed the existence of a strong thermodynamic size effect in the Cu-I2 reaction system, so that molar |ΔG| for 2... 

The synthesis of diamino triphenyl methanes from aniline and aromatic aldehydes was conducted in near critical water and supercritical water. The reaction parameters, such as temperature, density, and reaction time, have been studied. Significant acceleration of the condensation reaction of aniline and aromatic aldehydes can be achieved by using high temperature water, especially near the critical point, in the absence of any acid catalysts. It has been demonstrated that high temperature water act effectively in the place of conventional acid catalysts  

Thorium dioxide (thoria) nano-particle was synthesized by employing supercritical water (SCW) as an excellent reaction environment for hydrothermal crystallization of metal oxide particles. This method is ideal for production of ultrafine powder having controlled stoichiometry, high quality, purity and crystallinity. The nano-crystalline thoria was prepared in a stainless steel (316 L) autoclave, fed with an aqueous solution of Th(NO 3) 4.5H 2O as a reactant and took place under SCW condition up to 450 °C for 45 min. The product was recovered and characterized by X-Ray Diffraction (XRD), Thermal Gravimetry Analysis (TG/DTA) and Brunauer, Emmett and Teller (BET) surface area analysis. The... 

In this study, the essential oil of aerial parts species of a plant called Spearmint was extracted by CO 2 to optimize the results of the supercritical extraction process. In order to achieve maximum total yield extraction and SF-CO 2 concentration, tests were done in a laboratorial pilot considering the Taguchi method under following condition: pressure. 90,100,140,170 bar, temperature. of 35, 40, 45, 50 °C, mean particles size: 250,500,710,1000 μm, flow rate 1,3,5,8 ml/s and dynamic time 30,50,90,120 min. The optimizing conditions for SCE and SF-CO 2 concentration are: 90 bar, 45 °C, 500 μm, 5 ml/s, 120 min and 90 bar, 35 °C, 250 μm, 1 ml/s, 30 min. SCE total yield and CO 2 concentration... 

The solubility of acetaminophen in SuperCritical-Carbon Dioxide (SC- CO 2) with and without menthol as a cosolvent was measured at various temperatures (313, 328 and 343) K, and within pressures ranging from (10 to 25) MPa. It should be stated that the cosolvent, menthol, has chiral isomers with different melting points. Therefore, the effects of both menthol (I) with a lower melting point and menthol (II) with a higher melting point, as cosolvents on the solubility of acetaminophen in SC- CO 2, were studied. The experimental data collected in this work were obtained using a static flow apparatus. The experiments were replicated at least three times and the data reported are the average of... 

Ultrafine particles of paracetamol were produced by Rapid Expansion of Supercritical Solution (RESS). The experiments were conducted to investigate the effects of extraction temperature (313353K), extraction pressure (1018MPa), preexpansion temperature (363403K), and postexpansion temperature (273323 K) on particles size and morphology of paracetamol particles. The characterization of the particles was determined by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Liquid Chromatography/Mass Spectrometry (LC-MS) analysis. The average particle size of the original paracetamol was 20.8m, while the average particle size of paracetamol after nanonization via the... 

An efficient method for the synthesis of 4-amino-5-pyrimidinecarbonitriles by three-component reaction of malononitrile, aldehydes and N-unsubstituted amidines, under aqueous conditions, using CuO nanoparticles as catalyst is reported. The protocol offers advantages in terms of higher yields, short reaction times, and mild reaction conditions, with reusability of the catalyst  

In this paper, a new correlation to calculate the thermal conductivity of supercritical carbon dioxide based on 668 data points from the literature is introduced. The proposed correlation is valid in temperature range from 310 to 960 K, and pressures range between 7.4 and 210 MPa. The average absolute error of the model was found to be 2.7 and 2.4% in the comparison with the literature and NIST data respectively, which demonstrates superiority of the model over other methods  

One of the key factors in drug's efficacy is the value of their bioavailability that increases by the reduction of particle size through improvement of dissolution rate. In this study, raloxifene particle size was reduced by Rapid Expansion of Supercritical Solution (RESS). The effect of extraction temperature (40-80 °C), extraction pressure (10-18 MPa) and spray distance (5-10 cm) were investigated on size and particle size distribution of the nanoparticles. Particles were characterized using X-ray diffraction (XRD), Fourier Transform Infrared Analysis (FTIR), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and Dynamic Light Scattering (DLS). The average size of... 

By a single-step supercritical hydrothermal synthesis method, yttrium oxide nanoparticles were successfully prepared without additional treatment. Yttrium oxide nanoparticles were employed as an adsorbent to study the adsorption of some heavy metal ions. This study revealed that nano structure yttrium oxide was an effective adsorbent for removal of lead ions from aqueous solutions