pinecone/core-2020-05-10-deduplication huggingface dataset:
Nonlinear dynamics of ion concentration polarization in porous media: The leaky membrane model

The conductivity of highly charged membranes is nearly constant, due to counterions screening pore surfaces. Weakly charged porous media, or “leaky membranes,” also contain a significant concentration of coions, whose depletion at high current leads to ion concentration polarization and conductivity shock waves. To describe these nonlinear phenomena in the absence of electro-osmotic flow, a simple leaky membrane model is formulated, based on macroscopic electroneutrality and Nernst–Planck ionic fluxes. The model is solved in cases of unsupported binary electrolytes: steady conduction from a reservoir to a cation-selective surface, transient response to a current step, steady conduction to a flow-through porous electrode, and steady conduction between cation-selective surfaces in cross flow. The last problem is motivated by separations in leaky membranes, such as shock electrodialysis. The article begins with a tribute to Neal Amundson, whose pioneering work on shock waves in chromatography involved similar mathematics
A system-theoretic, control-inspired view and approach to process safety

Accidents in the process industry continue to occur, and we do not seem to be making much progress in reducing them (Venkatasubramanian, 2011). Postmortem analysis has indicated that they were preventable and had similar systemic causes (Kletz, 2003). Why do we fail to learn from the past and make adequate changes to prevent their reappearance? A variety of explanations have been offered; operators' faults, component failures, lax supervision of operations, poor maintenance, etc. All of these explanations, and many others, have been exhaustively studied, analyzed, “systematized” into causal groups, and a variety of approaches have been developed to address them. Even so, they still occur with significant numbers of fatalities and injured people, with significant disruption of productive operations and frequently extensive destruction of the surrounding environment, both physical and social
Simultaneous synthesis of heat exchanger networks with pressure recovery: optimal integration between heat and work

The optimal integration between heat and work may significantly reduce the energy demand and consequently the process cost. This paper introduces a new mathematical model for the simultaneous synthesis of heat exchanger networks (HENs) in which the pressure levels of the process streams can be adjusted to enhance the heat integration. A superstructure is proposed for the HEN design with pressure recovery, developed via generalized disjunctive programming (GDP) and mixed-integer nonlinear programming (MINLP) formulation. The process conditions (stream temperature and pressure) must be optimized. Furthermore, the approach allows for coupling of the turbines and compressors and selection of the turbines and valves to minimize the total annualized cost, which consists of the operational and capital expenses. The model is tested for its applicability in three case studies, including a cryogenic application. The results indicate that the energy integration reduces the quantity of utilities required, thus decreasing the overall cost.The authors acknowledge financial support from the Brazilian agency “Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – CAPES”, under process 10758/12-7. The Spanish Ministry of Science and Innovation and Ministry of Economy and Competitiveness, under project CTQ2012-37039-C02-02, are gratefully acknowledged
Wicking and evaporation of liquids in porous wicks: a simple analytical approach to optimization of wick design

Wicking and evaporation of volatile liquids in porous, cylindrical wicks is investigated where the goal is to model, using simple analytical expressions, the effects of variation in geometrical parameters of a wick, such as porosity, height and bead-size, on the wicking and evaporation processes, and find optimum design conditions. An analytical sharp-front flow model involving the single-phase Darcy’s law is combined with analytical expressions for the capillary suction pressure and wick permeability to yield a novel analytical approach for optimizing wick parameters. First, the optimum beadradius and porosity maximizing the wicking flow-rate are estimated. Later, after combining the wicking model with evaporation from the wick-top, the allowable ranges of bead-radius, height and porosity for ensuring full saturation of the wick are calculated. The analytical results are demonstrated using some highly volatile alkanes in a polycarbonate sintered wick
Comminution process modeling based on the monovariate and bivariate direct quadrature method of moments

Population balance equations (PBE) applied to comminution processes are commonly based on selection and breakage functions, which allow the description of changes of particle‐size distributions vs. time. However, other properties, such as the particle strength, also influence the grinding kinetics. A bivariate PBE was developed and resolved by the direct quadrature method of moments. This equation includes both the particle size and strength, the latter of which is defined as the minimum energy required for breakage. The monovariate case was first validated by comparing the predicted moments with those calculated from the size distributions given by an analytical solution of the PBE derived for specific selection and breakage functions. The bivariate model was then compared with a discretized model to evaluate its validity. Finally, the benefit of the bivariate model was proven by analyzing the sensitivity of some parameters and comparing the results of the monovariate and bivariate cases
Optimal experiment design for nonlinear dynamic (bio)chemical systems using sequential semidefinite programming

In this paper optimal experiment design for parameter estimation in nonlinear dynamic (bio)chemical processes is studied. To reduce the uncertainty in an experiment a suitable measure of the Fisher information matrix or variance-covariance matrix has to be optimized. In this work, novel optimization algorithms based on sequential semidefinite programming are proposed. The sequential semidefinite programming approach has specific advantages over sequential quadratic programming in the context of optimal experiment design. First of all, it guarantees on a matrix level a decrease of the uncertainty in the parameter estimation procedure by introducing a linear matrix inequality. Second, it allows an easy formulation of E-optimal designs in a direct optimal control optimization scheme. Finally, a third advantage of semidefinite programming is that problems involving the inverse of a matrix can be easily reformulated. The proposed techniques are illustrated in the design of experiments for a fed-batch bioreactor and a microbial kinetics case study. © 2014 American Institute of Chemical Engineers AIChE J, 2014status: publishe
In situcharacterization of floc morphology by image analysis in a turbulent Taylor-Couette reactor

Flocculation of bentonite was performed in a turbulent Taylor–Couette reactor under various shear rates. Image processing enabled to determine various morphological characteristics of individual flocs. Not only their mean values but also their distributions were studied under various hydrodynamic conditions. Relevant properties were selected. The temporal evolution of radius of gyration and circularity distributions was monitored during the flocculation process. Although size and shape are obviously correlated, this article points out that their dependency to hydrodynamics is different, showing that flocs of similar sizes produced under different hydrodynamic conditions exhibit different shapes. The sizes are calibrated by the turbulence as the double radius of gyration is close to Kolmogorov microscale, whereas the circularity seems correlated to the rotation speed. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2389–2403, 201
Mass-Transfer Enhancement by a Reversible Chemical Reaction Across the Interface of a Bubble Rising Under Stokes Flow

Mass transfer around a bubble rising in a liquid under Stokes regime is investigated when a reversible chemical reaction, A !B, is taken into account. Four dimensionless parameters control the interfacial transfer rate: the Peclet and Damkohler numbers, the ratio of the diffusion coefficient of both species, and the reaction equilibrium constant. The € mass-transfer equations are solved numerically with a finite element technique. A boundary layer approach is also proposed and solved with a coupled technique of finite difference and Chebyshev-spectral method. The equilibrium constant and the ratio of diffusion coefficients have a strong influence on the coupling between the chemical reaction and mass transfer leading to an increase of the Sherwood number. The interaction between the chemical reaction and advection is clearly established by the simulations. Conditions corresponding to Peclet number larger than the Damkohler number reduces the effect of the chemical reaction
Kinetics of CO2 Absorption by Aqueous 3-(methylamino)propylamine Solutions: Experimental Results and Modeling

Experimental data and a model for the initial kinetics of CO2 into 3-(methylamino)propylamine (MAPA) solutions are presented in work. MAPA has been tested as an activator for tertiary amines with encouraging results. The measurements were performed in a string of discs contactor and, as no initial kinetics data are available in literature, additional measurements were carried out and in a wetted wall column. The obtained overall mass-transfer coefficients from both apparatuses are in reasonable agreement. To obtain values for the observed kinetic constant, inline image, the experimental results were interpreted using a two-film mass-transfer model and invoking the pseudo-first order assumption. Needed experimental values for density, viscosity, and Henry's law coefficient for CO2 were measured and are given. The results indicate that MAPA is almost twice as fast as piperazine, eight times faster than 2-(2-aminoethyl-amino)ethanol (AEEA), and 15 times faster than monoethanolamine, when comparing unloaded 1 M solutions at 25°C. The observed kinetic constant was modeled using the direct mechanism. The final expression for inline image can be applied for any concentration and temperature within the experimental data range, and, together with the presented physical data, comprises a complete model for calculating absorption fluxes. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3792–3803, 2014© Wiley. This is the authors’ accepted and refereed manuscript to the article
Gas-liquid flow modeling in columns equipped with structured packing

The modeling of gas–liquid flow in distillation columns equipped with structured packing has been dealt. The devices are seen as bistructured porous media, and a macroscale model is proposed taking into account this specific geometry. In this model, the two liquid films, one-per-sheet, are treated separately and are allowed to exchange matter at the vicinity of the contact points between corrugated sheets. The model emphasizes mechanisms that lead to the liquid radial dispersion effects: a main part comes from the geometry itself, another part is due to the capillary effects. A particular attention is paid to model these phenomena from a macroscale point of view. Finally, the simulation results are confronted to tomography imaging within a lab-scale column and show a qualitative good agreement of the liquid distribution
A numerical study of dynamic capillary pressure effect for supercritical carbon dioxide-water flow in porous domain

This is the accepted version of the following article: DAS, D.B. ... et al., 2014. A numerical study of dynamic capillary pressure effect for supercritical carbon dioxide-water flow in porous domain. AIChE Journal, 60 (12), pp. 4266-4278, which has been published in final form at http://dx.doi.org/10.1002/aic.14577Numerical simulations for core-scale capillary pressure (Pc)–saturation (S) relationships have been conducted for a supercritical carbon dioxide-water system at temperatures between 35°C and 65°C at a domain pressure of 15 MPa as typically expected during geological sequestration of CO2. As the Pc-S relationships depend on both S and time derivative of saturation (∂S / ∂t) yielding what is known as the ‘dynamic capillary pressure effect’ or simply ‘dynamic effect’, this work specifically attempts to determine the significance of these effects for supercritical carbon dioxide-water flow in terms of a coefficient, namely dynamic coefficient (τ). The coefficient establishes the speed at which capillary equilibrium for supercritical CO2-water flow is reached. The simulations in this work involved the solution of the extended version of Darcy’s law which represents the momentum balance for individual fluid phases in the system, the continuity equation for fluid mass balance, as well as additional correlations for determining the capillary pressure as a function of saturation, and the physical properties of the fluids as a function of temperature. The simulations were carried for 3D cylindrical porous domains measuring 10 cm in diameter and 12 cm in height. τ was determined by measuring the slope of a best-fit straight line plotted between (i) the differences in dynamic and equilibrium capillary pressures (Pc,dyn – Pc,equ) against (ii) the time derivative of saturation (dS/dt), both at the same saturation value. The results show rising trends for τ as the saturation values reduce, with noticeable impacts of temperature at 50% saturation of aqueous phase. This means that the time to attain capillary equilibrium for the CO2-water system increases as the saturation decreases. From a practical point view, it implies that the time to capillary equilibrium during geological sequestration of CO2 is an important factor and should be accounted for while simulating the flow processes, e.g., to determine the CO2 storage capacity of a geological aquifer. In this task, one would require both the fundamental understanding of the dynamic capillary pressure effects for supercritical CO2-water flow as well as τ values. These issues are addressed in this article
Enhanced performance of supercritical fluid foaming of natural-based polymers by deep eutetic solvents

Natural deep eutetic solvents (NADES) are defined as a mixture of two or more solid or liquid components, which at a particular composition present a high melting point depression becoming liquids at room temperature. NADES are constituted by natural molecules and fully represent the green chemistry principles. For these reasons, the authors believe that the submit manuscript is a highly valuable contribution to the field of green chemistry and chemical engineering. For the first time, the possibility to use NADES as enhancers of supercritical fluid tecnology is revealed.The research leading to these results has received funding from Fundacao da Ciencia e Tecnologia (FCT) through the project ENIGMA-PTDC/EQU-EPR/121491/2010 and the project PEst-C/EQB/LA0006/2013. The funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no REGPOT-CT2012-316331-POLARIS and from Project "Novel smart and biomimetic materials for innovative regenerative medicine approaches (Ref.: RL1 - ABMR - NORTE-01-0124-FEDER-000016)" cofinanced by North Portugal Regional Operational Programme (ON.2 - O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF) and FEDER are also acknowledged. Marta Martins, Rita Craveiro and Alexandre Paiva are grateful for financial support from Fundacao da Ciencia e Tecnologia (FCT) through the grants BIM/PTDC/EQU-EPR/121491/2010/ENIGMA and SFRH/BPD/44946/2008
Natural Giesekus fluids: shear and extensional behaviour of food gum solutions in the semi-dilute regime

The shear and extensional behaviour of two aqueous gum solutions, namely (i) 1-20 g/L guar gum and (ii) κ/ι-hybrid carrageenan solutions (5-20 g/L), are shown to exhibit Giesekus-fluid behaviour when in the semi-dilute regime. In this regime a common set of Giesekus fluid parameters described both shear and extensional behaviour. A new analytical result describing the extension of a Giesekus fluid in the filament stretching geometry is presented. This also gave reasonable predictions of the Trouton ratio. Higher concentration guar solutions, in the entangled regime, yielded different Giesekus fluid parameters for extension to those for simple shear. The extensional data for all concentrations of both gums collapsed to a common functional form, similar to that reported for cake batters; the limits of the new filament thinning expression provide insight into this behaviour.The authors acknowledge financial support (POS-A/2012/116) for MDT from Xunta de Galicia’s Consellería de Cultura, Educación e OrdenaciónUniversitaria of Spain and the European Union’s 
European Social Fund. Helpful and insightful comments from the reviewers are also gratefully acknowledged.This is the accepted manuscript version. It will become accessible 12 months after publication. The final version is available from Wiley at http://dx.doi.org/10.1002/aic.14611
Evaporation of pinned droplets containing polymer – an examination of the important groups controlling final shape

Controlling the final shape resulting from evaporation of pinned droplets containing polymer, is important in the fabrication of P-OLED displays by inkjet printing. Typically, a coffee - ring shape arises, due to the pinning and associated outward capillary flow. For operational reasons, this is undesirable – a flat topography is required. The aim of this work is to understand the important groups governing the shape, to provide a practical guide to ink selection. The theory presented is based on a thin-film lubrication model. The governing equations are solved numerically and continuously track the lateral progression of a liquid/gel front. A large capillary number or large ratio of initial to maximal polymer volume fraction can suppress the coffee-ring. White light interferometry is used to confirm these findings experimentally.This research has been funded by the Engineering & Physical Sciences Research Council, UK and CASE studentship funding from Cambridge Display Technology Ltd., UK. The authors thank Dr Mark Dowling of Cambridge Display Technology Ltd., for help with the experimental setup.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/aic.14777
Rigorous design of distillation columns using surrogate models based on Kriging interpolation

The economic design of a distillation column or distillation sequences is a challenging problem that has been addressed by superstructure approaches. However, these methods have not been widely used because they lead to mixed-integer nonlinear programs that are hard to solve, and require complex initialization procedures. In this article, we propose to address this challenging problem by substituting the distillation columns by Kriging-based surrogate models generated via state of the art distillation models. We study different columns with increasing difficulty, and show that it is possible to get accurate Kriging-based surrogate models. The optimization strategy ensures that convergence to a local optimum is guaranteed for numerical noise-free models. For distillation columns (slightly noisy systems), Karush–Kuhn–Tucker optimality conditions cannot be tested directly on the actual model, but still we can guarantee a local minimum in a trust region of the surrogate model that contains the actual local minimum.The authors gratefully acknowledge the financial support of the Ministry of Economy and Competitiveness of Spain, under the project CTQ2012-37039-C02-02
Application of the functional renormalization group method to classical free energy models

A simple functional renormalization group method is presented to correct the behavior of classical free energy models near the critical point. This approach is applied to the Soave-Redlich-Kwong equation of state to illustrate its ability to better reproduce the phase behavior of simple fluids and to understand the influence of its parameters on the shape of the vapor-liquid phase diagram. The method is then extended to account for the correlations induced by intramolecular bonds. It is then applied to a first order thermodynamic perturbation theory for chain fluids to examine fluids composed of linearly bonded Lennard-Jones atoms. Unlike previous approaches for applying renormalization group corrections to chain fluids, this is able to accurately reproduce the critical point without predicting an overly flat liquid-vapor coexistence region
A filtration model for prediction of local flux distribution and optimization of submerged hollow fiber membrane module

© 2015 American Institute of Chemical Engineers. A filtration mathematical model was developed on the basis of complete mass balance and momentum balance for the local flux distribution prediction and optimization of submerged hollow fiber membrane module. In this model, the effect of radial permeate flow on internal flow resistance was considered through a slip parameter obtained from the local flux experiments. The effects of fiber length, inside diameter, and average operating flux on local flux distribution were investigated using this model. The predicted results were in good agreement with the experimental data obtained from literature. It was also found that the asymmetry distribution of local flux could be intensified with the increase of average operating flux and fiber length, but slowed down with the increase of fiber inside diameter. Furthermore, the simulation coupled with energy consumption analysis could efficiently predict and illustrate the relationship between fiber geometry and water production efficiency
Systematic design of an extractive distillation for maximum-boiling azeotropes with heavy entrainers

Extractive distillation is one of the most attractive approaches for separating azeotropic mixtures. Few contributions have been reported to design an extractive distillation for separating maximum-boiling azeotropes and no systematic approaches for entrainer screening have been presented. A systematic approach to design of two-column extractive distillation for separating azeotropes with heavy entrainers has been proposed. A thermodynamic feasibility analysis for azeotropes with potential heavy entrainers was first conducted. Then, five important properties are selected for entrainer evaluation. Fuzzy logic and develop membership functions to calculate attribute values of selected properties have been used. An overall indicator for entrainer evaluation is proposed and a ranking list is generated. Finally, the top five entrainers from the ranking list have been selected and use process optimization techniques to further evaluate selected entrainers and generate an optimal design. The capability of the proposed method is illustrated using the separation of acetone–chloroform azeotropes with five potential entrainers