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A two-level full factorial design was used to analyze several factors involved in PSF–GO–Pebax thin film nanocomposite membranes development. Permeate flux was chosen as a single response for four possible factors: Pebax selective layer concentration, amount of GO load to Pebax selective layer, Pebax–GO selective layer thickness, and amount of GO load to PSF substrate. The study is aimed at factors interaction and contribution towards the highest permeation flux via FFD and RSM approach. R2 obtained from the ANOVA is 0.9937 with Pebax concentration as the highest contributing factor. Pebax concentration–amount of GO load to PSF substrate is the only interaction contributing to the highest flux. A regression analysis concluded the study with model development and an optimized condition for the membrane design., Chemical engineering; Membrane; Transport process; Computer-aided engineering; Films; Thin film; Nanomaterials; Composite film; Hydrophilic enhancement; ANOVA; Optimization

The evaluation of a new air water generator (AWG) based on absorption and reverse osmosis is described. For the evaluation, an aqueous lithium bromide solution has been selected from a wide range of liquids as the absorbent. At high salt mass fractions, the aqueous lithium bromide solution has a low vapour pressure and a high osmotic pressure. The low vapour pressure ensures that the water vapour can be absorbed from the air, but the high osmotic pressure leads to high pressures over the membrane. Due to the high osmotic pressures, several reverse osmosis membrane modules are necessary and salt solution has to be present on both sides of the membrane, which leads to an additional inlet on the permeate side. Models for the absorber, the reverse osmosis membrane module and the complete multi-stage reverse osmosis system have been developed in Python. The model of the complete system has then been used to simulate the performance of the AWG at different boundary conditions. The simulations have shown that based on the defined assumptions, extracting water from the air with absorption and reverse osmosis is possible and that the energy demand per litre of pure water is similar to AWG systems which use condensation., + ID der Publikation: hslu_82593 + Art des Beitrages: Wissenschaftliche Medien + Jahrgang: 6 + Sprache: Englisch + Letzte Aktualisierung: 2021-12-09 09:37:44

Solidifiers are dry, granular hydrophobic polymers that form physical bonds with hydrocarbons by molecular interactions (hydrogen bonding, London forces), and are used to immobilize hydrocarbon spill propagation and dispersion. CIAgent© is a non-toxic, proprietary polymer blend listed as an “Oil Solidifier” on the EPA's National Contingency Plan Product Schedule for use on hydrocarbon spills in the navigable waterways of United States. CIAgent solidifies the liquid hydrocarbons through a rapid transformation into a cohesive rubber-like inert mass upon contact and retains the liquid for easier removal and disposal. The objective of this paper is to determine the effectiveness of the solidifier with a variety of hydrocarbon liquids that could be encountered in an oil spill scenario. The effectiveness of the solidifier was characterized in terms of the application rate, temperature change, solubility parameters and solidification time for a variety of hydrocarbon liquids (e. g., gasoline, diesel fuel, crude oil) that could be encountered by measuring the heat of solidification using a solution calorimeter. A thermogram was obtained and the heat of solidification was calculated using the temperature difference upon solidification. The temperature change and the degree of swelling in the solidifier were used to determine the solubility parameter of the solidifier (6.77 Hildebrands). The heat of solidification value was used to determine the ease and speed of the solidification of the hydrocarbon liquids. Solidification times ranged from 40 to 120 s for the liquids tested. The average application ratio in weight of solidifier to weight of hydrocarbon ranged was 3.35., Chemical engineering; Environmental Chemical Engineering; Transport Process; Adsorption; Water Treatment; Environmental Hazard; Solidification; Hydrocarbon; calorimeter; polymer; spill remediation

Low liquid-loading flow frequently occurs during the transport of gas products in various industries, such as in the Oil & Gas, the Food, and the Pharmaceutical Industries. Even small amounts of liquid can have a significant effect on the flow conditions inside the pipeline, such as increased pressure loss, pipe wall stresses and corrosion, and liquid holdup along the pipeline. However, most studies that analyze this type of flow only use atmospheric pressures and horizontal 1-in or 2-in pipes, which do not accurately represent the range of operating conditions present in industrial applications. Therefore, this study focused on modeling low liquid-loading flow in medium-sized (6–10 in) pipes, using CFD simulations and experimental data from the University of Tulsa, and then applying it to real operating conditions from a Colombian gas pipeline. An acceptable difference was observed between experimental and CFD data, both for the liquid holdup (18%) and for the pressure drop (12%). Variables like pressure drop and wall shear stress increase with phase velocity, operating pressure, and pipe inclination. Liquid holdup increases with liquid velocity but decreases with all other factors. The relation of flow variables with phase velocities is of particular interest: Doubling the gas velocity decreased holdup 70% and increased pressure drop tenfold. On the other hand, the presence of the liquid phase seems to be more influential on process variables than its exact flowrate; the introduction of the liquid phase to a single-phase gas causes an increase in pressure loss by a factor of three, but doubling the liquid velocity only increases the pressure loss by a further 30%., Chemical engineering; Petroleum engineering; Transport process; Computational fluid dynamics; Petroleum industry; Natural gas; CFD; Low liquid-loading flow; Pipeline transport; Pressure drop; Flow assurance.

Calcium fluoride (CaF2) nanoparticles with various terbium (Tb) doping concentrations were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and alternating current (AC) impedance measurement. The original shape and structure of CaF2 nanoparticles were retained after doping. In all the samples, the dominant charge carriers were electrons, and the F&minus, ion transference number increased with increasing Tb concentration. The defects in the grain region considerably contributed to the electron transportation process. When the Tb concentration was less than 3%, the effect of the ionic radius variation dominated and led to the diffusion of the F&minus, ions and facilitated electron transportation. When the Tb concentration was greater than 3%, the increasing deformation potential scattering dominated, impeding F&minus, ion diffusion and electron transportation. The substitution of Ca2+ by Tb3+ enables the electron and ion hopping in CaF2 nanocrystals, resulting in increased permittivity.

To achieve the integrity of solid particles coated by water phase (S/W/O) compound droplets, it is important to investigate the transport process of the compound droplets in the horizontal straight channel. The experimental results show that the integrity is significantly influenced by the flow rates and density difference. The water (W) phase is observed to be peeled off from the surface of the particles (polystyrene (PS) shells), mainly caused by the slip velocity of the W phase and the density mismatching among three phases. During the peeling off process, a relative motion between the solid (S) and W phases initially occurs, causing a decrease of the distance (δ) between them, and then, the PS shell is driven to pass through the W/O interface under the action of drag force and net gravity. It is also found that increasing flow rates of both phases contributes to obtaining integrated compound droplets. A boundary that separates the integrated from damaged compound droplets also exits when the fluid properties are fixed. Above the line of the boundary, compound droplets with integrity are prepared. Moreover, the absolute optimum density matching between the S and W phases is less than 0.003 g/cm3, while that between the W and oil (O) phases is less than 0.005 g/cm3.

Analysis of ‘entropy generation’ is an important strategy to build, optimize and operate the heat exchange systems within their maximum operating efficiency. Porous rhombic cavities with various inclination angles, φ and various thermal aspect ratios, A, have been considered for the numerical investigation of thermal processing of various fluids (Prandtl number, Pr = 0.015 and 1000) in the range of Darcy number (Da = 10−3–10) due to its extensive energy related applications. The effect of A and φ for various governing parameters during convection are discussed in detail via heat transfer irreversibility (Sθ) and fluid friction irreversibility, Sψ. At lower A, the entropy generation in the cavity is dominated by both Sθ and Sψ for all φs irrespective of Da and Pr. As A increases, Sθ as well as Sψ decreases for all φs which in turn decreases Stotal with A irrespective of Da and Pr. The total entropy generation (Stotal) is found to be lower for φ = 30° and higher for φ = 75° for all Pr and Da. Analysis of variations of Beav with A for higher Da (Da = 10) indicates that, entropy generation is highly fluid friction dominant irrespective of φ and A. Lesser entropy generation (Stotal) with larger heat transfer rate ( Nu b ¯ ) and reasonable heat transfer rate ( Nu b ¯ ) occurs for Pr = 0.015 and Pr = 1000, respectively at φ = 30° cavities with all A irrespective of Da. Current work attempts to analyze energy efficient thermal convection strategies and role of thermal aspect ratio within porous rhombic enclosures based on entropy generation minimization vs heat transfer rates for various fluids.

A numerical model is developed for investigating the evolution of fracture permeability in a coupled fracture-matrix system in the presence of fracture-skin with simultaneous colloidal and bacterial transport, by taking into account the effects of thermal stress and silica precipitation/dissolution, which is computed using linear reaction kinetics. The non-linear coupled equations are numerically modeled using the fully implicit finite difference method and a constant continuous source is adopted while modeling thermal, contaminant, colloidal and bacterial transport. Due to co-colloid bacterial transport under non-isothermal conditions, in a coupled fracture-skin-matrix system, the fracture apertures vary spatially, with a corresponding pressure variation for a constant discharge. A series of numerical experiments were conducted for analyzing the spatial variation of fracture aperture in response to the combined effects of thermal stress, silica precipitation/dissolution, and simultaneous colloidal and bacterial transport in the presence of the fracture-skin. The simulation results suggest that temperature and contaminant concentration of the mobile fluid within the fracture increases with reduction in initial fracture aperture. The pattern of variation followed by the fracture aperture is nearly the same in the presence and absence of bacterial transport but the magnitude of the fracture aperture is low under the influence of bacterial transport. The variation in the fracture aperture resulting from precipitation-dissolution and thermoelastic stress is significant when the fracture aperture is very low and reduces with increment in fracture aperture. The variation in fracture aperture and pressure remains the same for both undersaturated and supersaturated fluid entering the fracture due to the influence of bacterial transport at the inlet of the fracture. � 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.

A numerical study of the interaction between flow, reactions and thermal effects in a planar two dimensional model of a catalytic convertor is presented. A typical catalytic convertor consists of an inlet manifold, a catalytic monolith and an outlet manifold. The catalytic monolith is modeled as a multi-channel structure. Two different planar 2D geometries are compared: a full-scale geometry with 85 channels and a reduced-scale model with 21 channels. The diverging diffuser section of the inlet manifold, which lies immediately upstream the catalytic monolith, induces flow non-uniformity along the transverse direction. The flow immediately upstream of the multi-channel monolith is highly non-uniform. However, the frictional pressure drop in the individual channels tends to reduce this non-uniformity within individual channels. A "flow distribution index" - ratio of actual flow-rate in a channel to the ideal expected flow-rate if the flow was uniform - is defined to numerically characterize the flow mal-distribution across the various channels in the monolith. The velocity and scale effects are analyzed. Higher inlet velocities induce more flow non-uniformity. Catalytic oxidation of CO represented by power-law kinetics is employed to study the role of flow distribution. The flow distribution affects the conversion in the catalytic convertor, with different conversions in central and peripheral channels of the monolith. The net conversion from the device is marginally lower than what is predicted by single channel simulations with an assumption of uniform flow distribution. The thermal effects due to heat losses and reactions also in turn affect flow distribution. The flow tends to be more uniform when heat losses are included in the non-adiabatic simulations for the geometric parameters and kinetics considered in this work. � 2011 Elsevier Ltd.

Microwaves are shown to provide higher heating rates, however, the destructive interference of propagating waves leads to poor heating performance for specific lengths of samples. Enhanced processing rates for all length scales due to microwave incidence would be important for material processing and current work on discrete material processing involving intermediate air layers with microwave incidence attempts to fill the gap. Simulation studies involve electric field, microwave power and temperature which are obtained based on microwave propagation and energy balance equations. A preliminary investigation on average power absorption within beef (highly lossy) and bread (low dielectric loss) samples vs sample thickness exhibits a few local minima of average power which forms the basis of investigation on the role of discrete samples. The thickness of air layer plays a significant role to dramatically alter the interference of waves and power absorption within each sample layer. It is observed that three discrete sample layers (case 3) exhibit larger heating rate than that within the continuous sample (case 1) for specific sample thicknesses. In general, case 2 samples (with one intermediate air layer) show lesser power or heating enhancement in the presence of either one side or both sides microwave incidence. Based on two factors, 'large heating rate' and 'optimal thermal runaway', the efficient heating strategy may be derived for both high and low lossy food substances. � 2013 Elsevier Ltd.

We present an experimental and theoretical characterization of single cigar-shaped nanopores with pH-responsive carboxylic acid and lysine chains functionalized on the pore surface. The nanopore characterization includes (i) optical images of the nanostructure obtained by FESEM; (ii) different chemical procedures for the nanopore preparation (etching time and functionalizations; pH and electrolyte concentration of the external solution) allowing externally tunable nanopore responses monitored by the current-voltage (I-V) curves; and (iii) transport simulations obtained with a multilayer nanopore model. We show that a single, approximately symmetric nanopore can be operated as a reconfigurable diode showing different rectifying behaviors by applying chemical and electrical signals. The remarkable characteristics of the new nanopore are the sharp response observed in the I-V curves, the improved tunability (with respect to previous designs of symmetric nanopores) which is achieved because of the direct external access to the nanostructure mouths, and the broad range of rectifying properties. The results concern both fundamental concepts useful for the understanding of transport processes in biological systems (ion channels) and applications relevant for tunable nanopore technology (information processing and drug controlled release). © 2012 American Chemical Society., P.R., J.C., and S.M. acknowledge the financial support from the Ministry of Science and Innovation of Spain, Materials Program (Project Nos. MAT2009-07747) and FEDER. M.A., Q.H.N., S.N, and W.E. gratefully acknowledge financial support by the Beilstein-Institut, Frankfurt/Main, Germany, within the research collaboration NanoBiC, and Prof. C. Trautmann (GSI, Department of Materials Research) for support with irradiation experiments.

The morphology of poly(N-cyanoethylpyrrole) has been controlled through the polymerization process. This polymer has been prepared by anodic polymerization, chemical oxidative polymerization in emulsion medium, and layer-by-layer templating polymerization. Anodic polymerization using LiClO4 as supporting electrolyte provides compact films, in which the oxidation degree is controlled through the thickness, useful for the microdetection of dopamine. Chemical polymerization using FeCl3 as oxidant agent results in very well-defined microspheres with porous internal structure, which may be useful in molecular loading and transport processes. Finally, the layer-by-layer templating technique produces core−shell particles of controlled size and thickness. Moreover, these core−shell particles can be easily converted in hollow microspheres by removing the template

We propose a unified physical framework for transport in variably saturated porous media. This approach allows fluid flow and solute migration to be treated as ensemble averages of fluid and solute particles, respectively. We consider the cases of homogeneous and heterogeneous porous materials. Within a fractal mobile-immobile (MIM) continuous time random walk framework, the heterogeneity will be characterized by algebraically decaying particle retention-times. We derive the corresponding (nonlinear) continuum limit partial differential equations and we compare their solutions to Monte Carlo simulation results. The proposed methodology is fairly general and can be used to track fluid and solutes particles trajectories, for a variety of initial and boundary conditions., Comment: 12 pages, 9 figures

The present article analyzes the dissipation characteristics of the direct contact condensation (DCC) phenomenon that occurs when steam is injected into a water tank at a subsonic speed using a new modeling approach for the entropy generation over the calculation domain. The developed entropy assessment model is based on the local equilibrium hypothesis of non-equilibrium thermodynamics. The fluid flow and heat transfer processes are investigated numerically. To describe the condensation and evaporation process at the vapor-liquid interface, a phase change model originated from the kinetic theory of gas is implemented with the mixture model for multiphase flow in the computational fluid dynamics (CFD) code ANSYS-FLUENT. The CFD predictions agree well with the published works, which indicates the phase change model combined with the mixture model is a promising way to simulate the DCC phenomenon. In addition, three clear stages as initial stage, developing stage and oscillatory stage are discriminated from both the thermal-hydraulic results and the entropy generation information. During different stages, different proportion of the entropy generation rate owing to heat transfer, viscous direct dissipation, turbulent dissipation and inner phase change in total entropy generation rate is estimated, which is favorable to deeper understanding the irreversibility of DCC phenomenon, designing and optimizing the equipment involved in the process.

An outline is given of some of the steps which in the last ten years have led to an understanding of many of the properties of conduction and valence bands in non-crystalline materials. The concept of a mobility edge is described and some of the experimental evidence for its existence. A discussion is given of the nature of states in the gap, thought of as deep donors or acceptors. These pin the Fermi energy and act as recombination centres. A distinction is made between materials such as silicon or germanium with fourfold co-ordination and those like As2Te3 or SiO 2, where for the chalcogen (Te or O) co-ordination is twofold; for the former an electron in a deep state produces only moderate distortion of the lattice, for the latter the distortion is large. Photoluminescence and other properties of chalcogenides ave discussed in terms of a recent model of charged dangling bonds. It is suggested that free holes in As2Te3 and As 2Se3 are not self-trapped but that in SiO2 they are. Finally the nature of the optical absorption edge in SiO2 is contrasted with that in a soda glass in terms of a model of self-trapped excitons.

A numerical model is developed for describing the transport of virus in a fracture-matrix coupled system with fracture-skin. An advective dispersive virus transport equation, including first-order sorption and inactivation constant is used for simulating the movement of viruses. Implicit finite-difference numerical technique is used to solve the coupled non-linear governing equations for the triple continuum model consisting of fracture, fracture-skin and the rock-matrix. A varying grid is adopted at the fracture and fracture-skin interface to capture the mass transfer. Sensitivity analysis was performed to investigate the effect of various properties of the fracture-skin as well as viruses on the virus concentration in the fractured formation with fracture-skin. Simulation results suggest that the virus concentration in the fracture decreases with increment in the fracture-skin porosity, fracture-skin diffusion coefficient, mass transfer coefficient, inactivation constant and sorption distribution coefficient, and with reduction in the fracture aperture. � 2012, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.