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Under different transport mechanisms, blood flow dynamics, heavily linked to the flow shear rate conditions, in “lab-on-a-chip” (LOC) systems are found to result in varying transport phenomena. This Review examines the blood flow patterns in LOC systems through the role of viscoelastic properties such as dynamic blood viscosity and elastic behavior of the red blood cells. The study of blood transport phenomena in LOC systems through key parameters of capillary and electro-osmotic forces is provided through experimental, theoretical, and numerous numerical approaches. The disturbance triggered by electro-osmotic viscoelastic flow is particularly discussed and applied in the enhancement of the mixing and separating capabilities of LOC devices handling blood and other viscoelastic fluids for future research opportunities. Furthermore, the Review identifies the challenges in the numerical modeling of blood flow dynamics under the LOC systems, such as the call for more accurate and simplified blood flow models and the emphasis on numerical studies of viscoelastic fluid flow under the electrokinetic effect. More practical assumptions for zeta potential conditions while studying the electrokinetic phenomena are also highlighted. This Review aims to provide a comprehensive and interdisciplinary perspective on blood flow dynamics in microfluidic systems driven by capillary and electro-osmotic forces.

A comprehensive kinetic Monte Carlo algorithm has been developed to investigate the formation process of a polyurethane/poly(methyl methacrylate) (PU/PMMA) interpenetrating polymer network (IPN), in which a component independent strategy is proposed to perform the simulation of simultaneous polycondensation and free radical polymerization. An empiric diffusion model based on the mass fraction of polymer is used to quantify the effect of diffusional limitations on MMA polymerization. Results show that the presence of acrylic monomers has little impact on the formation rate of PU, but the presence of the PU network can accelerate the polymerization of MMA. In addition, the effects of component mass ratio, acrylic cross-linker concentration, and [NCO]/[OH] ratio on the IPN formation kinetics are investigated based on the kinetic model. It is believed that the as-developed modeling strategy can be extended to other IPN systems and provide a better understanding of the interactions between chemically independent networks. [ABSTRACT FROM AUTHOR]

Partially water-soluble monomers achieve phase equilibrium between aqueous and dispersed phases, and the interphase mass transfer plays a significant role in suspension polymerization. This work developed a computational fluid dynamics model to simulate the liquid-liquid suspension polymerization process. Complex multiphase flow behaviors and multiscale polymer properties were simultaneously simulated using the combination of an Eulerian-Eulerian two-phase flow model, an atom transfer radical polymerization kinetics model, a population balance model (PBM), and an interphase transfer model. The simulation results for monomer conversion, molecular weight (M n), polydispersity index (PDI), and Sauter mean diameter (d 32) agreed well with the experimental data, thereby validating the soundness of the multiscale model. The proposed model was then employed to predict key variables of the polymerization system. The coupled model can benefit the optimization and scale-up of suspension polymerization reactors with such multiscale characteristics. [ABSTRACT FROM AUTHOR]

ABSTRACT Electrostatics is an inevitable phenomenon in fluidization processes and granular flow, where collisions between particulates and walls with different materials occur. In this work, a two-dimensional computational fluid dynamics model based on the Eulerian-Eulerian approach was applied and coupled with a first-principles electrostatic model to describe the gas-solid two-phase flow behavior in a fluid catalytic cracking (FCC) riser reactor under the electrostatic conditions. The coupled model was used to predict the main gas-solid flow distribution parameters in the FCC riser, such as electric potential, particle volume fraction, gas-phase temperature, and gas-phase component fractions. The simulation results showed that the electrostatic had a significant influence on the particle distribution in the bottom dense region of the FCC riser, whereas it had a weak influence in the upper dilute region at the cold-flow conditions. The simulation results also showed that the electrostatic had a weak influence on the particle concentration, gas-phase temperature, and lump concentration distributions when the cracking reaction was considered. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A coupled-single-particle and Monte Carlo model was used to simulate propylene polymerization. To describe the effects of intraparticle transfer resistance on the polymerization kinetics, the polymeric multilayer model (PMLM) was applied. The reaction in each layer of the PMLM was described with the Monte Carlo method. The PMLM was solved together with the Monte Carlo model. Therefore, the model included the factors of the mass- and heat-transfer resistance as well as the stochastic collision nature of the polymerization catalyzed with single-site-type/multiple-site-type catalysts. The model presented results such as the polymerization dynamics, the physical diffusion effect, and the polymer molecular weight and its distribution. The simulation data were compared with the experimental/actual data and the simulation results from the uniform Monte Carlo model. The results showed that the model was more accurate and offered deeper insight into propylene polymerization within such a microscopic reaction-diffusion system. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

In industrial loop reactors for catalytic propylene polymerization, the reactor pressure can influence the polymerization rate, feed flow rate, and product properties, especially safe operation of the reactor. To predict the pressure change during polymerization and check the performance of pressure-relief devices in response to emergency accidents, a dynamic model was developed based on mass and energy balances as well as thermodynamics and kinetics. In this model, the pressure was related to the temperature by a state equation for high-pressure liquid. The pipeline equations of the reactors described by the conservation of mechanical energy were incorporated into the model to better predict the pressure. In addition to the pressure, the model can also predict other variables, such as temperature, slurry density, and solids holdup in the reactors. Dynamic data from an industrial plant were used for model validation. Furthermore, the application of the model was demonstrated by simulating several typical emergency accidents. [ABSTRACT FROM AUTHOR]

Well‐defined poly(dimethylsiloxane‐b‐styrene) diblock copolymers were prepared by reversible addition–fragmentation chain‐transfer (RAFT) polymerization. Monohydroxyl‐terminated polydimethylsiloxane was modified to form a functional polydimethylsiloxane/macro‐RAFT agent, which was reacted with styrene to form the diblock copolymers. The chemical compositions and structures of the copolymers were characterized by proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography. The surface properties and morphology of the copolymers were investigated with static water contact‐angle measurements, X‐ray photoelectron spectroscopy, transmission electron microscopy, and atomic force microscopy, which showed a low surface energy and microphase separation surfaces that were composed of hydrophobic domains from polydimethylsiloxane segments. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [ABSTRACT FROM AUTHOR]

In this study, the kinetics of propylene polymerization catalyzed with the fourth heterogeneous Ziegler-Natta catalyst is studied. More than one type of active site is present in the propylene polymerization based on an analysis of the GPC curves. A multiple active site kinetic model (MSmodel) is proposed by using Monte Carlo technique. Good agreements in the polymerization kinetics are achieved for fitting the kinetic profiles with the MSmodel. In addition, the MSmodel is used to describe the dynamic evolutions of the active sites and their effects on the propylene polymerization. The simulated results indicate that different types of active sites have different polymerization kinetics and the site type can affect the propylene polymerization kinetics. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [ABSTRACT FROM AUTHOR]

In the present study, a reactor design for the direct preparation of dichloropropanol (DCP) from glycerol (GLY) is presented. As an optimum design, a reactive distillation (RD) column in which the second chlorination of GLY occurs during the direct preparation of DCP from GLY has been introduced. Using a simple equilibrium mathematical model of RD, a pilot plant scale column is designed. Furthermore, the whole preparation process of DCP from GLY used the optimum RD column as the central unit is simulated by using an advanced software tool, namely ASPEN PLUS. The pilot plant realization of the whole preparation process is presented and its results are compared with the theoretical prediction. On the basis of the pilot plant data and simulated results, a new technology of DCP production has been designed. [ABSTRACT FROM AUTHOR]

Direct preparation of 1,3-dichloro-2-propanol from glycerol is carried out in a batch reactor using acetic acid catalyst at 363−393 K. The analytical technique, gas chromatography, is employed in order to follow the time evolution of the reagents. The kinetic model of the process is developed. Furthermore, the model parameters of the process are also determined by data fitting. The results show that direct preparation follows the SN2 mechanism. A kinetic model corresponding to the mechanism is proposed in this work. The experimental results show that the kinetic model agrees well with the experiments. [ABSTRACT FROM AUTHOR]

The article reports on a study regarding the mathemical model of the molecular weight distribution (MWD) of polypropylene produced in a loop reactor. The study found out that the simulated MWD data of the polymers created in steady-state polymerization corresponds to the actual data gathered from a certain plant. The plant data in start up processes also corresponds to the simulated weight-average molecular weight data. The influence of the operation parameters on the molecular weight distribution produced in both the steady-state and dynamic polymerizations can be simulated with the use of the mathematical model.

A comprehensive polymerization kinetics model that includes site formation, chain initiation, chain propagation, chain transfer and chain deactivation elementary reactions was incorporated into the three‐fluid computational fluid dynamics (CFD) model to describe the polymer properties in the gas–liquid–solid three‐phase polyethylene fluidized bed reactor. The effect of operating conditions on polyethylene properties was firstly discussed. Furthermore, due to the importance and complexity of scaling up three‐phase reactors, the incorporated CFD model was then employed to investigate the scale‐up influence, which indicates that the difference of flow hydrodynamics in the reactor due to scale‐up effect will result in the difference of polymerization reaction rate. [ABSTRACT FROM AUTHOR]

Two improved multigrain models (MGMs) for preparing homopolypropylene and long chain branched polypropylene via propylene polymerization using silica-supported metallocene or dual function metallocene as catalysts are presented in this paper. The presented models are used to predict the intraparticle flow fields involved in the polymerizations. The simulation results show that the flow field distributions involved are basically identical. The results also show that both polymerization processes have an initiation stage and the controlling step is reaction-diffusion-reaction with the polymerization proceeding. Furthermore, the simulation results show that the intraparticle mass transfer resistance has significant effect on the polymerization, but the heat transfer resistance can be ignored. [ABSTRACT FROM AUTHOR]

A two-dimensional (2D) pseudo-homogeneous reactor model was developed to simulate the performance of fixed bed reactors for catalytic coupling reaction of carbon monoxide to diethyl oxalate. Reactor modeling was performed using a comprehensive numerical model consisting of two-dimensional coupled material and energy balance equations. A power law kinetic model was applied for simulating the catalytic coupling reaction with considering one main-reaction and two side-reactions. The validity of the reactor model was tested against the measured data from different-scale demonstration processes and satisfactory agreements between the model prediction and measured results were obtained. Furthermore, detailed numerical simulations were performed to investigate the effect of major operation parameters on the reactor behavior of fixed bed for catalytic coupling reaction of carbon monoxide to diethyl oxalate, and the result shows that the coolant temperature is the most sensitive parameter. [ABSTRACT FROM AUTHOR]

In this study, a two-stage fluidized bed reactor (TS-FBR) was designed as a new technology to produce diethyl oxalate (DEO) from carbon monoxide (CO) based on the catalytic coupling reaction. Computational fluid dynamics (CFD) approach was adopted to obtain the detailed flow field, the bubble behaviors in the TS-FBR, and further demonstrate the feasibility of the TS-FBR used in producing DEO from CO. Furthermore, the whole preparation process of DEO from CO using the optimum TS-FBR as the central unit is simulated using an advanced software tool, realizing the proper matching of coupling reaction and regeneration reaction. As a result, the realization of the whole preparation process is presented. [ABSTRACT FROM AUTHOR]