Heat transfer enhancement inside an eccentric cylinder with an inner rotating wall using porous media: a numerical study

Journal of Thermal Analysis and Calorimetry - Porous media insert is a simple technique to enhance heat transfer, which has been used in different applications. This useful passive improvement...     

New hybrid Cartesian cut cell/enriched multipoint flux approximation approach for modelling and quantification of structural uncertainties in petroleum reservoirs

Efficient and profitable oil production is subject to make reliable predictions about reservoir performance. However, restricted knowledge about reservoir rock and fluid properties and its geometrical structure calls for history matching in which the reservoir model is calibrated to emulate the field observed history. Such an inverse problem yields multiple history‐matched models, which might result in different predictions of reservoir performance. Uncertainty quantification narrows down the model uncertainties and boosts the model reliability for the forecasts of future reservoir behaviour. Conventional approaches of uncertainty quantification ignore large‐scale uncertainties related to reservoir structure, while structural uncertainties can influence the reservoir forecasts more significantly compared with petrophysical uncertainty. Quantification of structural uncertainty has been usually considered impracticable because of the need for global regridding at each step of history matching process. To resolve this obstacle, we develop an efficient methodology based on Cartesian cut cell method that decouples the model from its representation onto the grid and allows uncertain structures to be varied as a part of history matching process. Reduced numerical accuracy due to cell degeneracies in the vicinity of geological structures is adequately compensated with an enhanced scheme of a class of locally conservative flux continuous methods (extended enriched multipoint flux approximation method or extended EMPFA). The robustness and consistency of the proposed hybrid Cartesian cut cell/extended EMPFA approach are demonstrated in terms of true representation of geological structures influence on flow behaviour. Significant improvements in the quality of reservoir recovery forecasts and reservoir volume estimation are presented for synthetic model of uncertain structures. Copyright © 2015 John Wiley & Sons, Ltd.     

The effect of electric field geometry on the performance of electromembrane extraction systems: Footprints of a third driving force along with migration and diffusion

The distribution of electric field vectors was first calculated for electromembrane extraction (EME) systems in classical and cylindrical electrode geometries. The results showed that supported liquid membrane (SLM) has a general field amplifying effect due to its lower dielectric constant in comparison with aqueous donor/acceptor solutions. The calculated norms of the electric field vector showed that a DC voltage of 50 V can create huge electric field strengths up to 64 kV m⁻¹ and 111 kV m⁻¹ in classical and cylindrical geometries respectively. In both cases, the electric field strength reached its peak value on the inner wall of the SLM. In the case of classical geometry, the field strength was a function of the polar position of the SLM whereas the field strength in cylindrical geometry was angularly uniform. In order to investigate the effect of the electrode geometry on the performance of real EME systems, the analysis was carried out in three different geometries including classical, helical and cylindrical arrangements using naproxen and sodium diclofenac as the model analytes. Despite higher field strength and extended cross sectional area, the helical and cylindrical geometries gave lower recoveries with respect to the classical EME. The observed decline of the signal was proved to be against the relations governing migration and diffusion processes, which means that a third driving force is involved in EME. The third driving force is the interaction between the radially inhomogeneous electric field and the analyte in its neutral form.     

Encapsulation of palladium chloride using 2‐formylbenzoic acid supported by Fe3O4 nanoparticles modified with SiO2 and propylamine,its characterization and its application for Suzuki coupling reaction

A magnetically separable heterogeneous nanocatalyst, Fe₃O₄@SiO₂(CH₂)₃N―CH―Ar@Pd(0), was simply prepared and characterized using various techniques. The catalytic activity of this nanocatalyst was evaluated via the Suzuki–Miyaura cross‐coupling reaction of aryl halides with phenylboronic acid under various experimental conditions such as kind of base, solvent and temperature. This nanocatalyst is completely magnetically recoverable because of the superparamagnetic behaviour of Fe and can be reused with sustained selectivity and activity.     

Ultrasound-assisted,low-solvent and acid/base-free synthesis of 5-substituted 1,3,4-oxadiazole-2-thiols as potent antimicrobial and antioxidant agents

Molecular Diversity - One of the goals of green chemistry is to use environmentally friendly solvents or remove and reduce the volume of harmful spent solvents. In this study, a novel process for...     

Synthesis of new functionalized reduced graphene oxide quantum dot composite for high-performance NO2 gas sensor

Research on Chemical Intermediates - In this research, synthesis of a novel magnetic 2-naphthalenesulfonic acid-grafted reduced graphene oxide quantum dot (Fe3O4-rGOQD-naphthalene-2-SO3H) via a...     

Calculation of Viscosity and Diffusion Coefficients for Two Binary Gaseous Mixtures Using the Semi-empirical Inversion Method

The accurate reduced potential energies for two binary gas mixtures including benzene-methanol and methane-tetrafluoromethane at low density have been obtained by direct inversion of the viscosity collision integral equations. The kinetic theory along with the extended principle of corresponding-states has been used to calculate the viscosity and dif-fusion coefficients over a wide range of temperature and composition. Good agreements between calculated and experimental data are obtained.     

The effects of Knudsen-dependent flow velocity on vibrations of a nano-pipe conveying fluid

In this paper, we investigate the effect of nano-flow on vibration of nano-pipe conveying fluid using Knudsen (Kn). We use Euler–Bernoulli plug-flow beam theory. We modify no-slip condition of nano-pipe conveying fluid based on Kn. We define a Kn-dependent flow velocity. We consider effect of slip condition, for a liquid and a gas flow. We reformulate Navier–Stokes equations, with modified versions of Kn-dependent flow velocity. We observe that for passage of gas through nano-pipe with nonzero Kn, the critical flow velocities decreased considerably as opposed to those for zero Kn. This can show that ignoring Kn effect on a gas nano-flow may cause non-conservative design of nano-devices. Furthermore, a more impressive phenomenon happens in the case of clamped-pinned pipe conveying gas fluid. While we do not observe any coupled-mode flutter for a zero Kn, we can see the coupled-mode flutter, accompanying the second-mode divergence, for a nonzero Kn.     

Fluorosis Caused Cellular Apoptosis and Oxidative Stress of Rat Kidneys

As the strongest electronegative element, fluorine can stimulate the production of superoxide radicals in cells. In view of the important roles of kidneys in bone metabolism, the authors analyzed the quantitative pathomorphological characteristics of renal damage and the potential cellular apoptosis and oxidative stress mechanisms in rats treated with excessive fluoride. Wistar rats were exposed to 50 mg F^-(110.5 mg NaF)/L, 100 mg F^-(221.0 mg NaF)/L and 150 mg F^-(331.5 mg NaF)/L in drinking water for 70 and 140 d, respectively. Microscope with image analysis was used to quantitate pathomorphological changes in renal tissues of the rats. Reactive oxygen species(ROS), the cell cycle and apoptosis of renal cells were measured by flow cytometry and TUNEL technique(terminal deoxynucleotidyl transferase dUTP nick end labeling), respectively. The ion concentrations in serum and renal functional parameters were detected by automatic biochemical analyzer. Quantitative analysis results demonstrate the expanded Bowman’s space of glomerulus and obvious dilatation of renal tubule. TUNEL technique revealed that NBT/BCIP (nitro blue tetrazolium/5-bromo-4-chloro-3′-indolylphosphate, p-toluidine salt)-staining positive apoptotic cells selectively located in medullocortical junction areas. The data suggest that renal damage in chronic fluorostic rats is associated with the cellular apoptosis and oxidative stress.     

Buckling behavior of perfect and defective DWCNTs under axial, bending and torsional loadings via a structural mechanics approach

The buckling behavior of perfect and defective double-walled carbon nanotubes (DWCNTs) under axial compressive, torsional and bending loadings is investigated using a structural mechanics model. The effects of van der Waals (vdW) forces are further modeled using a nonlinear spring element. Critical buckling loads, critical buckling moments and the effects of vacancy defects were studied for armchair nanotubes with various aspect ratios. The results show that vacancy defects greatly reduce the critical buckling load of DWCNTs. The density of defects plays an important role in buckling of DWCNTs. The results of this numerical model are in good agreement with their comparable existing works.