The role of wettability of nonideal nozzle plate: From drop‐on‐demand droplet jetting to impact on solid substrate

The dynamics of drop‐on‐demand (DoD) droplet formation and subsequently impact on the solid substrate are investigated using a three‐dimensional (3‐D) multirelaxation‐time (MRT) pseudopotential lattice Boltzmann (LB) model. The wettability of nonideal nozzle plate and solid substrate is modeled by a geometric scheme within the LB framework. The dynamics of droplet formation are explored in a range of the inverse of Ohnesorge number , , and , and the Reynolds number , , and . For , no satellite droplet is observed and the wettability of nozzle plate greatly influences the velocity and length of jetting fluids. For , the filament breakup and recombination are observed. The moment of filament breakup is delayed with advancing contact angle increasing. For with , the primary and satellite droplets could not be recombined with and which agree with the literature. Whereas with , the recombination occurs. The dynamics of subsequent oscillating droplet impact on the substrate are similar to that of equilibrium droplet which could obtain high‐resolution printed features. Consequently, considering with large and numbers, the printable range could be extended which could help increase the printing frequency and boost the production outputs of inkjet printing. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2837–2850, 2018     

Framework for correlating the effect of temperature on nonelectrolyte and ionic liquid activity coefficients

A power‐law expression is proposed for correlating the temperature dependence of infinite‐dilution activity coefficients ( ) for nonelectrolyte solute–solvent binary pairs and for pairs including an ionic liquid: , where θ_ij = 0 for Lewis–Randall ideal solutions, θ_ij = 1 for classic enthalpy‐based Scatchard–Hildebrand regular solution and van Laar models, and ?5 < θ_ij < 5 for most real binaries. The exponent θ_ij is a function of partial molar excess enthalpy ( ) and entropy ( ) such that . Real binaries are classified into seven types corresponding to distinct domains of and θ_ij. The new method provides a framework for correlating phase‐equilibrium driven temperature effects for a wide variety of chemical and environmental applications. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3675–3690, 2014     

A rigorous method to evaluate the consistency of experimental data in phase equilibria. Application to VLE and VLLE

This work forms part of a broader study that describes a methodology to validate experimental data of phase equilibria for multicomponent systems from a thermodynamic‐mathematical perspective. The goal of this article is to present and justify this method and to study its application to vapor–liquid equilibria (VLE) and vapor–liquid–liquid equilibria (VLLE), obtained under isobaric/isothermal conditions. A procedure based on the Gibbs‐Duhem equation is established which presents two independent calculation paths for its resolution: (a) an integral method and (b) a differential method. Functions are generated for both cases that establish the verification or consistency of data, δψ for the integral test and δζ for the differential approach, which are statistically evaluated by their corresponding average values [ , ], and the standard deviations [ , ]. The evaluation of these parameters for application to real cases is carried out using a set of hypothetical systems (with data generated artificially), for which the values are adequately changed to determine their influence on the method. In this way, the requirements of the proposed method for the data are evaluated and their behavior in response to any disruption in the canonical variables (p,T, phase compositions). The conditions for thermodynamic consistency of data are: , , , and . In systems with VLLE, in addition to the previous criteria, must occur that: and . The new proposed method has been tested with a set of 300 experimental binary systems, biphasic and triphasic, obtained from published bibliography, and the results are compared with those of other tests commonly used for testing thermodynamic consistency. The results show that the greater rigor of the proposed method is mainly due to the simultaneous verification of various independent variables. As a result, the conditions for the new test are verified for fewer systems than using other tests mentioned in the literature (i.e., Fredenslund‐test and direct of Van Ness). Its unique application is sufficient to ensure the consistency of experimental data, without using other tests. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Maldistribution susceptibility of monolith reactors: Case study of glucose hydrogenation performance

In this work an ultrafast electron beam X‐ray modality was applied for the first time to characterize the gas–liquid Taylor flow inside each channel of an opaque honeycomb monolith structure ( ) for and . Significant spatial and temporal deviations in the phase holdup as well as in the gas bubble and liquid slug lengths were found. To evaluate the impact of Taylor flow maldistribution on the reactor performance, the data of more than unit cells were used to simulate the reactor productivity in the hydrogenation of glucose. The results verify that a monolith reactor solely designed by using superficial velocities and empirical correlations for gas bubble and liquid slug lengths fails significantly in achieving high product selectivity and the desired conversion. The developed methods are a solid base to design and select proper distributors ensuring the favorable flow configurations for specific chemical processes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4346–4364, 2016     

Experimental determination of maximum effective hydrodynamic stress in multiphase flow using shear sensitive aggregates

Maximum effective hydrodynamic stress, , responsible for the breakup of aggregates with size comparable to Kolmogorov eddies, was experimentally determined in an aerated stirred tank. The proposed method is based on the measurement of the maximum stable aggregates size consisting of poly(methyl methacrylate) nanoparticles. The fractal aggregates were broken under various operating conditions in an aerated stirred tank and calibrated with known flow conditions using contracting nozzles to convert the measured aggregate sizes into hydrodynamic stress. It was found that can vary substantially among studied conditions and its magnitude depends on the controlling mechanism including gas jet during bubble formation, bubble rise, bubble burst at the gas–liquid interface or the turbulence generated by the impeller. The measured values are in good agreement with literature data which supports the applicability of this method to characterize the maximum effective hydrodynamic stress in complicated multiphase flow. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1735–1744, 2015     

NMR spectroscopic study of chemical equilibria in solutions of formaldehyde,water, and butynediol

Liquid mixtures of formaldehyde, water, and butynediol are complex reacting multicomponent systems in which formaldehyde forms oligomers both with water and butynediol. ‐ and ‐NMR spectra of these mixtures are elucidated. The species distribution of the oligomers is quantitatively determined by ‐NMR spectroscopy. The measurements cover temperatures from 293 to 366 K, overall formaldehyde mass fractions from to , and overall butynediol mass fractions from to . A mole fraction‐based and an activity‐based model of the chemical equilibrium in the studied system are developed and chemical equilibrium constants are reported. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4442–4450, 2017     

Ionic Liquid Confined in Nafion: Toward Molecular‐Level Understanding

In this article, multiscale simulation methods were used to study structural and transport properties of Nafion–ionic liquid composite membranes that are novel proton conducting materials for fuel cells. Coarse‐grained model for 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim][BF₄]) ionic liquid was first developed in the framework of BMW‐MARTINI force field. Coarse‐grained simulation results of bulk [bmim][BF₄] ionic liquid show good agreement with all‐atom simulation results and experimental data. Nafion–[bmim][BF₄] composite membranes were then simulated using all‐atom and coarse‐grained models. Ionic liquid cluster formation inside Nafion was revealed by coarse‐grained simulations. Diffusion coefficients of both [bmim]⁺ cations and anions are reduced by one to two orders of magnitude depending on their concentrations in Nafion membrane. [Bmim]⁺ cations have faster self‐diffusion coefficient than anions, while this phenomenon is more pronounced when ionic liquids are confined in Nafion. This work provides molecular basis for understanding Nafion–ionic liquid composite membranes. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2630–2639, 2013     

Pressure drop through platinized titanium porous electrodes for cerium‐based redox flow batteries

The pressure drop, , across a redox flow battery is linked to pumping costs and energy efficiency, making fluid properties of the electrolyte important in scale‐up operations. The at diverse platinized titanium electrodes in Ce‐based redox flow batteries is reported as a function of mean linear electrolyte velocity measured in a rectangular channel flow cell. Darcy's friction factor and permeability vs. Reynolds number are calculated. Average permeability values are: 7.10 × 10^?4 cm² for Pt/Ti mesh, 4.45 × 10^?4 cm² for Pt/Ti plate + turbulence promoters, 1.67 × 10^?5 cm² for Pt/Ti micromesh, and 1.31 × 10^?6 cm² for Pt/Ti felt. The electrochemical volumetric mass transport coefficient, , is provided as a function of . In the flow‐by configuration, Pt/Ti felt combines high values with a relatively high , followed by Pt/Ti micromesh. Pt/Ti mesh and Pt/Ti plate gave a lower but poorer electrochemical performance. Implications for cell design are discussed. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1135–1146, 2018     

Effect of dead volumes on the performance of an industrial‐scale simulated moving‐bed Parex unit for p‐xylene purification

The cyclic steady state (CSS) of the industrial‐scale, seven‐zone, simulated moving‐bed (SMB) unit for p‐xylene (p‐x) purification (Parex unit) with three types of dead volumes—bed lines, push‐around and pump‐around circulation lines, and bed heads—is analyzed. In particular, the effects of the size and level of hydrodynamic dispersion of each dead volume on process performance and on its CSS are studied in detail. The circulation lines change the CSS behavior from ‐periodic to ‐periodic, where is the switching interval and is the number of columns in each adsorbent chamber. A high level of axial dispersion in the bed lines, characterized by Péclet numbers smaller than 100, affects the p‐x purity. Moreover, the bed lines lower the average p‐x concentration in the extract, which reduces the p‐x recovery. If the small time lags introduced by the circulation lines are neglected, it is possible to develop a detailed process model that considers the operation of the Parex unit over a single switching interval as opposed to a full cycle, and whose CSS solution can be efficiently computed using a full‐discretization approach. Finally, it is shown that the volume of the bed heads influences significantly the performance of the Parex unit, and that its impact on the location of the operating point with respect to the boundaries of the separation region can be approximately taken into account using the standard true moving‐bed‐SMB equivalence rules if they are corrected for the presence of extra interparticle fluid. © 2015 American Institute of Chemical Engineers AIChE J, 62: 241–255, 2016     

Mass transfer coefficient of tubular ultrafiltration membranes under high‐flux conditions

The effect of suction flow on the mass transfer coefficient of tubular ultrafiltration membranes, in particular that under a high‐flux condition, was studied. We pointed out that is proportional to under turbulent conditions, and that the proportional constant, b, exceeds 0.023 when the effect of suction flow is not negligible. We conducted the velocity variation method using ultrafiltration membranes with MWCOs of 20k and 100k and dextrans having molecular weights of 40,000 and 70,000 at the conditions, where exceeded . We demonstrated that the effect of suction flow includes not only flux but also the diffusion coefficient of solute, and that the ratio of the flux to the diffusion coefficient, expressed as , is an important index. Finally, we concluded that , when is smaller than , giving the Deissler equation itself, and that , when exceeds . © 2017 American Institute of Chemical Engineers AIChE J, 64: 1778–1782, 2018     

Forced convection boiling in a stator–rotor–stator spinning disc reactor

Boiling of a pure fluid inside the rotor–stator cavities of a stator–rotor–stator spinning disc reactor (srs‐SDR) is studied, as a function of rotational velocity ω, average temperature driving force and mass flow rate . The average boiling heat transfer coefficient h_b increases a factor 3 by increasing ω up to 105 rad s^?1, independently of and . The performance of the srs‐SDR, in terms of h_b vs. specific energy input ?, is similar to tubular boiling, where pressure drop provides the energy input. The srs‐SDR enables operation at Wm , yielding values of h_b not practically obtainable in passive evaporators, due to prohibitively high pressure drops required. Since h_b is increased independently of the superficial vapor velocity, h_b is not a function of and the local vapor fraction. Therefore, the srs‐SDR enables a higher degree of control and flexibility of the boiling process, compared to passive flow boiling. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3763–3773, 2016     

The influence of injection velocity and relaxation time on the spreading of tracers in viscoelastic liquids agitated by submerged,recirculating jets with low reynolds numbers

We provide experimental demonstration that the spread of tracer elements in a tank containing a viscoelastic liquid and agitated by a submerged jet pointing to the base of the tank can be influenced by the relaxation time of the liquid. We analyzed the temporal spreading of the boundary of a tracer‐front in two dimensions using flow visualization at early stages and found that for a given fluid, the evolution of the tracer‐front at various injection velocities follows a universal trajectory when considered on a normalized time scale of , where t is observation time, is injection velocity and is the effective diffusivity of the tracer elements in the medium. For a different fluid, at a given , the trajectory scales with the relaxation time of the fluid. The importance of relaxation time to the evolution of a tracer‐front is something previously unreported. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3132–3140, 2017     

Intensification of convective heat transfer in a stator–rotor–stator spinning disc reactor

A stator–rotor–stator spinning disc reactor is presented, which aims at intensification of convective heat‐transfer rates for chemical conversion processes. Single phase fluid‐rotor heat‐transfer coefficients h_r are presented for rotor angular velocities rad s^?1 and volumetric throughflow rates m³s^?1. The values of h_r are independent of and increase from 0.95 kWm^?2K^?1 at ω = 0 rad s^?1 to 34 kWm^?2K^?1 at ω = 157 rad s^?1. This is a factor 2–3 higher than values achievable in passively enhanced reactor‐heat exchangers, due to the 1–2 orders of magnitude larger specific energy input achievable in the stator–rotor–stator spinning disc reactor. Moreover, as h_r is independent of , the heat‐transfer rates are independent of residence time. Together with the high mass‐transfer rates reported for rotor–stator spinning disc reactors, this makes the stator–rotor–stator spinning disc reactor a promising tool to intensify heat‐transfer rates for highly exothermal chemical reactions. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2307–2318, 2015     

Removal of NO from flue gas using UV/S2 process in a novel photochemical impinging stream reactor

A novel photochemical impinging stream reactor was developed for the first time. Removal process of NO from flue gas using sulfate radical ( ·) and hydroxyl radical (·OH) from UV‐light activation of persulfate (UV/S₂ advanced oxidation process) was investigated in the novel reactor. Experiments were conducted to evaluate the effects of S₂ concentration, solution pH, UV power, solution temperature, liquid‐gas ratio, flue gas flow, NO, SO₂,and O₂ concentrations on removal of NO. Mechanism and kinetics of NO removal were also studied. The results show that increasing UV power, solution temperature, S₂ concentration, or solution circulation rate promotes NO removal. Increasing solution pH (1.2–11.9), NO concentration or flue gas flow weakens NO removal. O₂ concentration has no significant effect on NO removal. · and ·OH were the major active species for NO removal. Absorption rate equation and kinetic parameters of NO removal were obtained. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2968–2980, 2017     

Convective condensation in a stator–rotor–stator spinning disc reactor

Centrifugal intensification of condensation heat transfer in the rotor–stator cavities of a stator–rotor–stator spinning disc reactor (srs‐SDR) is studied, as a function of rotational velocity ω, volumetric throughflow rate , and average temperature driving force . For the current range of ω, heat transfer from the vapor bubbles to the condensate liquid is limiting, due to a relatively low gas–liquid interfacial area a_GL. For rad s^?1, a strong increase of a_GL, results in increasing the reactor‐average condensation heat transfer coefficient h_c from 1600 to 5600 W m^?2 K^?1, for condensation of pure dichloromethane vapor. Condensation heat transfer in the srs‐SDR is enhanced by rotation, independent of the vapor velocity. The intensified condensation comes at the cost of relatively high energy dissipation rates, indicating condensation in the srs‐SDR is more suited as a means to supply heat (e.g. in an intensified reactor‐heat exchanger), rather than for bulk cooling purposes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3784–3796, 2016     

Predicting effective conductivities based on geometric microstructure characteristics

Empirical relationships between effective conductivities in porous and composite materials and their geometric characteristics such as volume fraction , tortuosity τ and constrictivity β are established. For this purpose, 43 virtually generated 3D microstructures with varying geometric characteristics are considered. Effective conductivities are determined by numerical transport simulations. Using error‐minimization the following relationships have been established: and (simplified formula) with intrinsic conductivity σ₀, geodesic tortuosity and relative prediction errors of 19% and 18%, respectively. We critically analyze the methodologies used to determine tortuosity and constrictivity. Comparing geometric tortuosity and geodesic tortuosity, our results indicate that geometric tortuosity has a tendency to overestimate the windedness of transport paths. Analyzing various definitions of constrictivity, we find that the established definition describes the effect of bottlenecks well. In summary, the established relationships are important for a purposeful optimization of materials with specific transport properties, such as porous electrodes in fuel cells and batteries. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1834–1843, 2016     

Property prediction and consistency analysis by a reference series method

Data analysis and prediction of pure component properties of long‐chain substances is considered. The emphasis is on homologous series and properties for which insufficient data are available. A two‐stage procedure is recommended, whereby a linear (or nonlinear) quantitative structure–property relationship (QSPR) is fitted to a “reference” series, for which an adequate amount of precise data is available. This QSPR should represent correctly both the available data and the asymptotic behavior of the property. In the second stage a quantitative property‐property relationship (QPPR) is derived to represent the predicted property values of a “target” series in terms of the property values of the reference series. The procedure is applied for properties which are highly correlated with the number methylene groups in homologous series: and . It is shown that the method is very useful for consistency analysis of property data and enables a reliable prediction of and , and, thus, also of for long‐chain substances. © 2012 American Institute of Chemical Engineers AIChE J, 59: 420–428, 2013     

Heat transfer coefficient for condensation of steam on freely formed falling liquid jets

This article presents the research results of direct contact condensation of steam on freely formed falling liquid jets. After the comparison of experimental data and open literature correlations it was concluded that published correlations does not provide accurate coverage of experimental data. A new correlation was established in the following form © 2016 American Institute of Chemical Engineers AIChE J, 62: 2579–2584, 2016     

Rheological properties and structure of step‐ and chain‐growth gels concentrated above the overlap concentration

Cross‐linked polymeric gels are widely used in applications ranging from biomaterial scaffolds to additives in enhanced oil recovery. Despite this, fundamental understanding of the effect of polymer concentration and reaction mechanism on the scaffold structure is lacking. We measure scaffold properties and structure during gelation using multiple particle tracking microrheology. To determine the effect of concentration, we measure gelation as polymer interactions are increased in the backbone precursor solution: below, at and above the overlap concentration, . To determine structural changes due to the gelation mechanism, we measure gelation between the same polymers undergoing both step‐ and chain‐growth reactions using self‐assembling maleimide:thiol and photo‐initiated acrylate:thiol chemistries, respectively. We determine the critical relaxation exponent, n, a measure of structure. n decreases with increasing concentration, indicating a change from a percolated ( ) to a tightly cross‐linked network ( ). The gelation mechanism does not have a measurable effect on the scaffold structure. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3168–3176, 2018     

A positron emission particle tracking investigation of the scaling law governing free surface flows in tumbling mills

Positron Emission Particle Tracking (PEPT) measurements are used to track the flow of glass beads within a rotating drum fitted with (and without) lifter bars and operated in the cascading and cataracting Froude regimes. After converting the Lagrangian trajectories of a representative radio‐labeled glass bead (the tracer) into Eulerian fields under the ergodic assumption, the bed shape and kinematics are extracted for steady, fully developed flow conditions. Notwithstanding the azimuthal wall effects introduced by the lifter bars, we show a linear scaling of the local flowing layer thickness (h) with local depth‐averaged velocity and a constant average shear for direct measurements spanning the entire flowing layer (not just the central region), and high Froude regimes (cascading and cataracting) not previously investigated by scaling analysis in the literature. © 2016 American Institute of Chemical Engineers AIChE J, 63: 903–913, 2017