سال:1394 | دوره: | شماره: |تعداد مقالات:12

In this study, confined impinging liquid jets are used to produce nanoparticles of carbamazepine (CBZ). The effect of operating parameters, such as the kind of solvent, CBZ concentration, flow rate of solution and antisolvent on particle size, are experimentally investigated. The Scanning Electron Micrograph (SEM) photomicrographs show that nanodrug with smaller particle is achievable by using solvent with more supersaturation. Meanwhile, decreasing concentration causes the production of smaller particles in the range of 430 to 190nm and by increasing flow rate of solution, the particle size increases from 240 to 340 nm. Furthermore, the physical states of particles are investigated by Differential Scanning Calorimetry (DSC) test.

Although several methods for the preparation of 4 o propargyl indole derivatives have been published, this synthetic transformation is complicated by the tendency of 3 o propargyl alcohols to form allenium intermediates in acidic media. It is therefore a challenge to find an efficient method for the C-3 propargylation of indoles with 3o propargylic alcohols. In this paper we wish to report on the successful application of silica gel impregnated with NaHSO4 as catalyst for the preparation of 4 o propargyl indole derivatives.

Shape-selective methylation of naphthalene (NAPH) over SAPO-11 zeolite was carried out in a fixed-bed flow reactor under atmospheric pressure. Some zeolites, such as H-beta (Hb), HUSY and ZSM-5 were also evaluated for comparison with SAPO-11 zeolite. The results showed that SAPO-11 exhibited higher stability, higher selectivity of 2, 6-dimethylnaphthalene (2, 6-DMN), and higher 2, 6-/2, 7-DMN ratio than Hb, HUSY and ZSM-5. The improvement in catalytic performance of SAPO-11 is mainly attributed to the specific pore structure, weak acid strength and low acid amount on SAPO-11.

Batch experiments were conducted to study the adsorption behaviors of lead ion (Pb2+) onto ferrihydrites prepared using three different procedures which were characterized by textural analysis (BET). The adsorption removal of Pb2+ by the three ferrihydrites (called FH-1, FH-2 and FH-3, respectively) were compared, and FH-3 shows fast adsorption kinetics as well as high adsorption capacities, the adsorption properties of the three ferrihydrites for lead ion depend on the pH value and the optimal pH for Pb2+ adsorption of FH-3 is 6.0. The maximum adsorption capacity of lead ion on FH-3 is 13.75 mg/g and the adsorption isotherms followed Langmuir isotherm model better than the Freundlich isotherm model. The adsorption kinetic data could be described well by pseudo-second-order kinetic equation.

Synthetic dyes are among the most common contaminants of the environment. Therefore, the aim of this study was investigation the removal of Basic Blue 41 (BB41) and Methylene Blue (MB) from industrial effluents by useing raw and modified rice stems. In this study raw and modified rice stems treated chemically with Citric Acid (CA) and were used to explore the potentiality of rice stems for removal of BB41 and MB dyes. Effect of various parameters including pH, contact time, adsorbent dose and initial dye concentration on the adsorption were studied. To characterize the adsorbents, Scanning Electron Microscope (SEM) was used. The adsorbent surface functional groups identified with Fourier Transform InfraRed (FT-IR) spectroscopy. The applicability of the adsorption data was explained by Langmuir, Freundlich, Temkin and BET isotherms. The results showed that increasing of contact time and adsorbent dose, dye removal increases for both raw and modified adsorbents. Dye adsorption on to adsorbent increased with increasing of pH. Also the results indicated that dye removal efficiency was increased by decreasing initial dye concentration. Among studied isotherms, data were fitted well by Langmuir model (R2>0.98) for both raw and modified adsorbents. Also, adsorption kinetics were more fitted by pseudo second order model (R2>0.99).The results of the present work showed that rice stem was a good, low cost and effective adsorbent for removal of BB14 and MB from industrial effluents.

In this paper, experimental data on the drying kinetics of corn in a packed and fluidized bed are presented. Experimental research was conducted on a laboratory apparatus. Corn was used as a material because of its significance in agriculture and the food industry. An analysis of the influence of the operational parameters (the drying medium velocity i. e. the fluidization number, the drying medium temperature and the height of a packed bed) on the drying kinetics of corn, was performed. The experiment shows that increasing the fluidization number and the velocity of the drying medium, has no significant influence on the drying kinetics of corn, except during the initial period of drying.

The purpose of this study is to identify parameters influence on the particle deposition within fin and tube heat exchanger of air-conditioning systems by CFD analysis. First the basic sketch of periodic geometry drawn and meshing operation including boundary conditions was performed. Then the gas side properties and flow parameters were solved by ANSYS Fluent 14.5 software. Lagrangian equations used for modeling dispersed phase and effect of injecting various particle sizes evaluated by Rosin-Rammler model. Moreover turbulence effect was investigated using discrete random walk model. Consequently it is observed that deposition rate is highly affected by particles diameter in which leads to 90% deposition for particles over 30 µm in diameter.

In this paper, convection heat transfer of Al2O3-water nanofluid turbulent flow through internally ribbed tubes with different rib shapes (rectangular, trapezoidal and semi-circular) is numerically investigated. For each rib shape, the optimum geometric ratio and volume fraction were calculated using entropy generation minimization technique. The governing equations in steady state and axisymmetric form have been solved using Finite Volume Method (FVM) with the SIMPLE algorithm. A uniform heat flux was applied on the wall. A single-phase approach has employed to model the nanofluid. Nanoparticles size is 20 nm and nanoparticles volume fraction and Reynolds number were within the ranges of 0-5% and 10,000-35,000 respectively. Comparisons between the numerical results and experimental data show that among different turbulence models, k-e model with enhanced wall treatment gives better results. The results indicate that the heat transfer increases with nanoparticles volume fraction and Reynolds number but it is accompanied by increasing pressure drop. The simulations demonstrate that trapezoidal and semi-circular ribbed tubes have higher Nusselt number than the rectangular ribbed tubes with the same diameters. Correlations of heat transfer have obtained for different ribbed tubes. In evaluation of thermal performance and pressure drop, it is seen that the ribbed tubes with Al2O3-water nanofluid flow are thermodynamically advantageous. For each rib shape, the optimum geometric ratios are also presented.

In this research, the effect of micro turbulence on the flotation rate of quartz particles was investigated. The maximum particle Reynolds number (Rep) was obtained at 60.25 with a particle size of -500+420 µm, impeller speed of 900 rpm, bubble surface area flux of 10.21 1/s and micro scale turbulence size of 162 mm. When the micro turbulence size was equal to the particle size, the maximum flotation rate of coarse particles (Rep>10) was obtained at 1.47 1/min.

In this study the effect of nano sized silica particles (nano-SiO2) on the physical and mechanical properties of rice husk and Old Corrugated Container (OCC)-cement boards was investigated. Modulus Of Rupture (MOR), Modulus Of Elasticity (MOE), Internal Bonding Strength (IB), density, water absorption and thickness swelling after 24 hours immersion in water and hardness were measured. Results showed that rice husk-cement boards with 2% nano-SiO2 demonstrated the best physical and mechanical properties. It is related to better distribution and compaction of particles during compression without particles agglomerating. A higher property of 2%-nano-SiO2 content rice-husk-cement boards was confirmed by their higher hydration temperature. Addition of 3% nano-SiO2 to the mixture reduced the density because of both the substitution of denser cement particles by lighter nano-SiO2 particles and air-entrapment in the boards. Furthermore, Scanning Electron Microscopy (SEM) analyses showed that the optimum amount of nano-SiO2 (2%) can fill micro pores and make a uniform structure with a rough surface which improves properties of composite boards.

In this research the effect of conventional and ohmic pasteurization and storage time at different temperatures on some bioactive components of Aloe vera gel juice was investigated. Aloe vera gel juice was pasteurized conventionally and ohmically at 90oC for 1 min. The effect of pasteurization on vitamin C, total phenolic content and juice color was evaluated. The samples pasteurized conventionally, stored up to 30 days at 4 and 25oC. The effect of storage time on the stated components and also on glucomannan of the juice was evaluated. The results showed that pasteurization reduced vitamin C content and decreasing of vitamin C during ohmic heating was more than conventional heating. Total phenolic content increased during ohmic pasteurization more significant than conventional pasteurization. Browning index of samples after pasteurization increased but there were not any differences between browning index of samples pasteurized conventionally and ohmically. During storage at 4 and 25oC, total phenolic content remained stable, but vitamin C contents reduced from 84.47 to 54.96 at 4oC and 46.82 at 25oC mg vitamin C/100 g d.m and glucomannan contents reduced from 2.11 to 1.77 at 4oC and 1.71 g/L at 25oC.. Browning index increased significantly at both storage temperatures, which was more intensive at 25 than 4oC.

Residual gas saturation is one of the most important parameter in determining recovery factor of water-drive gas reservoir. Visual observation of processes occurring at the pore level in micromodels can give an insight to fluid displacements at the larger scale and also help the interpretation of production performance at reservoir scale. In this study experimental tests in a glass micromodel were used to determine the influence of the capillary number and pore morphology on the residual gas saturation in gas-liquid two-phase flow. The saturation of the phases was determined through recorded images in the micromodel. 2D modeling and simulation of this process is presented in this study and simulation results are verified by comparing to experimental results where sufficient agreement was confirmed. The simulation results indicate that pore morphology and capillary number have significant influence on the competition between frontal displacement and snap-off. Frontal displacement leads to high recovery and snap off causes gas entrapment. It is concluded that increasing the pore and throat sizes, increasing the coordination number and increasing angularity (decreasing half angle) result in reducing the residual gas amount. The results also indicate that residual gas saturation is not only a function of petrophysical property and pore morphology, but also it depends on flow rate and the experimental procedure. Residual gas saturation does not change significantly when Nc is less than 10-7.