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The paper considers the main problems of hydrodynamics of gas-liquid systems in relation to the developed process of crude hydrocarbon cracking in melts. The experimental study of hydrodynamic conditions was conducted by physical modeling at objects with similar physicochemical properties. The purpose of the research was to develop a methodology for determining the contact time and the interfacial area for the cracking process. Based on the experimental data, the formulas, the most suitable for the calculation of hydrodynamic parameters of sparging in melts were selected among the available in the literature. The boundaries of hydrodynamic regimes were defined. The experimental results showed the effect of the height of melt layer, diameter of the crude feeding tube, melt properties and space velocity of crude feeding on the time of bubbles ascent and the size of interfacial area. In laboratory experiments on the cracking of hydrocarbons in melts at the bubble mode of sparging (the specified gas velocity no more than 0.2 - 0.3 m/s), the contact time may vary from 0.1 to 0.5 s and a specific interfacial area from 50 to 1800 m2/m3. To achieve the maximum interfacial area, it is recommended to carry out the cracking of hydrocarbons in the melts in the foam mode at the gas phase velocity of 0.3 - 0.5 m/s. [ABSTRACT FROM AUTHOR]

The influence of a gas-liquid chemical reaction on the interfacial area produced in a contactor is analyzed. Two different amines were used to capture carbon dioxide by chemical absorption. The effects of the operation time, the amine used, the concentration interval, and the gas flow rate on typical hydrodynamic parameters used in bubble columns such as the gas holdup and the Sauter mean diameter were investigated. These parameters were used to determine the interfacial area value. Significant influences on the gas-liquid interfacial area were detected, mainly caused by the reaction rate intensity, the physicochemical properties of the liquid phase, and the gas flow rate fed to the contactor. [ABSTRACT FROM AUTHOR]

Highlights: [•] The lower contact angles led to increases in both P c and a nw . [•] The irreducible saturation increased as contact angle decreased. [•] The non-wetting phase breakthrough time varied with contact angle. [•] The energy dissipation factors varied with contact angle. [Copyright &y& Elsevier]

A three-dimensional multiphase numerical model was used to simulate the infiltration and dissolution of a dense nonaqueous phase liquid (DNAPL) release in two experimental flow cells containing different heterogeneous and well-characterized permeability fields. DNAPL infiltration was modeled using Brooks-Corey-Burdine hysteretic constitutive relationships. DNAPL dissolution was simulated using a rate-limited mass transfer expression with a velocity-dependent mass transfer coefficient and a thermodynamically based calculation of DNAPL-water interfacial area. The model did not require calibration of any parameters. The model predictions were compared to experimental measurements of high-resolution DNAPL saturations and effluent concentrations. The predicted concentrations were in close agreement with measurements for both domains, indicating that important processes were effectively captured by the model. DNAPL saturations greatly influenced mass transfer rates through their effect on relative permeability and velocity. Areas with low DNAPL saturation were associated with low interfacial areas, which resulted in reduced mass transfer rates and nonequilibrium dissolution. This was captured by the thermodynamic interfacial area model, while a geometric model overestimated the interfacial areas and the overall mass transfer. This study presents the first validation of the thermodynamic dissolution model in three dimensions and for high aqueous phase velocities; such conditions are typical for remediation operations, especially in heterogeneous aquifers. The demonstrated ability to predict DNAPL dissolution, only requiring prior characterization of soil properties and DNAPL release conditions, represents a significant improvement compared to empirical dissolution models and provides an opportunity to delineate the relationship between source zone architecture and the remediation potential for complex DNAPL source zones. [ABSTRACT FROM AUTHOR]

The dependence of the dielectric properties of micro- (m-) and nano- (n-) silver (Ag)/poly(vinylidene fluoride) (PVDF) composites on the Ag particle size was determined. The magnitude of dielectric constant and conductivity for the PVDF/n-Ag composites was much higher than that of the PVDF/m-Ag composites at the same Ag volume loading. Our results suggest that the percolative behaviors were quite different for the m- and n-systems owing to the Ag particle size effect. The dielectric property depends on the synergistic effects of interfacial area, interparticle distance, and interfacial adhesion, all of which are highly dependent on the Ag particle size. The increased interfacial area, reduced interparticle distance, and improved interfacial adhesion contributed to the better dielectric properties of the PVDF/n-Ag composites. [ABSTRACT FROM AUTHOR]

Abstract: Pilot plant data for CO2 capture with 8 m piperazine (PZ) were reconciled with an absorber model in Aspen Plus® using quantified error in pilot plant input data and a global correction to absorber performance parameters. Four global corrections were applied independently to adjust: interfacial area, liquid side mass transfer coefficient, solvent CO2 content, or solvent piperazine (PZ) content. Each of the four cases resulted in a reconciled model with pilot plant data and provides a potential route to quantifying and correcting measurement and experimental error as well as enhancing understanding of real absorber performance. The modified absorber model was then used to quantify the performance improvement due to implementation of a spray nozzle in the absorber intercooling loop. The spray nozzle added the equivalent of 7% to 20% more packing to the column as a function of the flow rate through the nozzle. [Copyright &y& Elsevier]

Previous studies of air-water interfacial areas in unsaturated porous media have often distinguished between interfacial area corresponding to water held by capillary forces between grains and area corresponding to water associated with solid surfaces. The focus of this work was on developing a better understanding of the nature of interfacial area associated with solid surfaces following drainage of porous media. Stereoscopic scanning electron microscopy was used to determine surface elevation maps for eight different surfaces of varying roughness. An algorithm was developed to calculate the true configuration of an air-water interface in contact with the solid surface as a function of capillary pressure. The algorithm was used to calculate surface-associated water configurations for capillary pressures ranging from 10 to 100 cm water. The results of the work show that, following drainage, the configuration of surface-associated water is dominated by bridging of macroscopic surface roughness features over the range of capillary pressures studied, and nearly all of the surface-associated water is capillary held. As such, the thicknesses of surface-associated water were found to be orders-of-magnitude greater than might be expected at the same capillary pressures based on calculations of adsorbed film thickness. The fact that capillary forces in air-water interfaces dominate surface-associated water configuration means that interface shapes are largely unaffected by microscopic surface roughness, and interfaces are considerably smoother than the underlying solid. As such, calculations suggest that microscopic surface roughness likely has minimal impact on the accuracy of surface-associated air-water interfacial areas determined by limited-resolution imaging methods such as computed microtomography. [ABSTRACT FROM AUTHOR]

Abstract: Heap bioleaching is gaining importance as an approach for the recovery of valuable metals (e.g. Cu2+) from low grade ores. In this process iron and/or sulfur oxidising microorganisms are used to aid the oxidation of base metal sulfides in the ore, thereby liberating the metal ions into solution. Leach performance is strongly influenced by the contacting of the leach solution and the ore particles. In order to better understand the distribution of the leaching solution on the pore scale in these heaps, Magnetic Resonance Imaging (MRI) was used to acquire images non-invasively of a section of an irrigated ore bed. This was made possible by the use of specialist MRI acquisition sequences suited to the magnetically heterogeneous environment as presented by the ore material. From the images we were able to determine the pore-occupancy of the liquid and gas phases and to provide novel measurement of the interfacial area between air, leach solution and ore. [Copyright &y& Elsevier]

Highlights: [•] Verification of the quantitative analysis of grain boundary fracture. [•] Breakage of cubic multiphase copper ore particles by slow compression. [•] Interfacial area was determined from XMT reconstructed images using the Marching Cube method. [•] Preferential grain boundary fracture only occurs at low energy dissipation rates. [•] Current results confirm initial results for 3mm cubes published previously. [Copyright &y& Elsevier]

Abstract: A numerical model of a two-phase flow in a plate microreactor was developed. The model is based on a computational fluid dynamics (CFD) approach and was constructed with the help of an open-source toolbox OpenFOAM, which utilizes a finite volume method to solve the equations of a fluid motion. A cold flow, i.e. a flow without a reaction and a mass transfer was considered in this study. The model was validated by comparing with experimentally measured hydrodynamic parameters: gas holdup and the interfacial area of gas bubbles inside the existing prototype. Validated model was used to test several proposed plate structures for the next prototype. The structure with the highest gas–liquid interfacial area was was chosen for the construction. [Copyright &y& Elsevier]

Abstract: The storage of supercritical carbon dioxide in deep saline aquifers requires new techniques to assess plume spreading, storage efficiencies and operational strategies after and during injections. In this work, a new class of reactive tracers (KIS tracers) planned to be used for the characterization of interfacial areas between supercritical CO2 and formation brine is presented. The implementation of a time-dependent hydrolysis reaction at the interface enables to investigate the development of the CO2/brine interface. Besides the basic concept for these novel tracers and the methodology for a suitable target molecular design, the desired tracer properties as well as the exemplary synthesis of first promising compounds are presented here. Additionally, the first experimental results of an analog study in a static two-phase batch system are shown and evaluated with a newly developed macroscopic model. Subsequently, the numerical forward modeling of different functions for the interfacial area change is described. The first results are promising and show the potential for new applications of KIS tracers after further research. [Copyright &y& Elsevier]

Vapor phase mass transfer is an important interphase transport process that dominates the overall transport phenomena in liquid-gas system in porous media. Volatilization of nonaqueous phase liquids (NAPLs) in porous media is such system that takes place during the remediation of volatile organic compound-contaminated soil using soil vapor extraction. Usually, interphase mass transfer coefficient is lumped together with the air-liquid interfacial area because of the inaccessibility to quantify this parameter due to the heterogeneous nature of the pore structure of the media and the morphology of the fluid distribution. In this paper, the air-liquid interfacial area is quantified using a simple method derived from pressure-saturation relationship in three glass bead media. A series of one-dimensional NAPL volatilization experiments were carried out in a horizontal column for the same porous media by using toluene as the single contaminant. Experiments were conducted for NAPL saturation range of 13.8 ~ 71 % and pore gas velocities of 0.1 ~ 2 cm/s, and lumped mass transfer coefficients were evaluated. Actual vapor phase mass transfer coefficients were calculated using corresponding air-liquid interfacial area for a specific NAPL saturation and characterized in dimensionless form for all porous media. Results revealed that the vapor phase mass transfer increases with pore gas velocities and grain sizes but decreases with NAPL saturation. [ABSTRACT FROM AUTHOR]

The behavior of chitosan and two kinds of chitosan derivatives in carbon dioxide absorption in a bubble column contactor is analyzed. The effects of absorption type (physical or chemical), polymer type, concentration, and liquid-phase physical properties on hydrodynamics (bubble size, gas holdup, and specific interfacial area) and mass transfer (absorption rate and mass transfer coefficient) are evaluated. [ABSTRACT FROM AUTHOR]

The gas-liquid volumetric mass transfer coefficient was determined by the dynamic oxygen absorption technique using a polarographic dissolved oxygen probe and the gas-liquid interfacial area was measured using dual-tip conductivity probes in a bubble column slurry reactor at ambient temperature and normal pressure. The solid particles used were ultrafine hollow glass microspheres with a mean diameter of 8.624 µm. The effects of various axial locations (height-diameter ratio = 1-12), superficial gas velocity ( uG = 0.011-0.085 m/s) and solid concentration ( εS = 0-30 wt.%) on the gas-liquid volumetric mass transfer coefficient kL aL and liquid-side mass transfer coefficient kL were discussed in detail in the range of operating variables investigated. Empirical correlations by dimensional analysis were obtained and feed-forward back propagation neural network models were employed to predict the gas-liquid volumetric mass transfer coefficient and liquid-side mass transfer coefficient for an air-water-hollow glass microspheres system in a commercial-scale bubble column slurry reactor. © 2012 Canadian Society for Chemical Engineering [ABSTRACT FROM AUTHOR]

Rigorous and consistent formulations of basic equations of interfacial area transport were derived using correlation functions of the characteristic function of each phase and velocities of each phase. The turbulent transport term of interfacial area concentration was consistently derived and related to the difference between the interfacial velocity and the averaged velocity of each phase. Constitutive equations of turbulent transport terms of interfacial area concentration were proposed for bubbly flow. New transport model and constitutive equations were developed for churn flow. These models and constitutive equations are validated by experimental data of radial distributions of the interfacial area concentration in bubbly flow and churn flow. [ABSTRACT FROM AUTHOR]

A microchannel was fabricated with glass tubes to investigate the effect of viscosity, surface tension, and flow rate on the liquid-liquid two-phase flow regime. Water and gasoil were selected as aqueous and organic working fluids, respectively. The two fluids were injected into the microchannel and created either slug or parallel profile depending on the applied conditions. The range of Reynolds and capillary numbers was chosen in such a way that neither inertia nor interfacial tension forces were negligible. Xanthan gum was used to increase viscosity and Triton X-100 (TX-100) and Sodium Dodecyl Sulfate (SDS) were used to reduce the interfacial tension. The results demonstrated that higher value of viscosity and flow rate increased interfacial area, but slug flow regime remained unchanged. The two surfactants showed different effects on the flow regime and interfacial area. Addition of TX-100 did not change the slug flow but decreased the interfacial area. In contrast, addition of SDS increased interfacial area by decreasing the slug's length in the low concentrations and by switching from slug to parallel regime at high concentrations. [ABSTRACT FROM AUTHOR]

Abstract: There are very few established correlations to predict the interfacial area concentration beyond the bubbly flow regime in cap-slug and churn-turbulent flow regimes. Present study shows a systematic approach to estimate the interfacial area concentration in bubbly, cap-slug and churn-turbulent flow regimes. Ishii and Mishima’s (1980) formulation and the two group approach for categorizing bubbles (Group-1: spherical or distorted bubble, Group-2: cap bubble) are used to estimate the interfacial area concentration. The key parameters in this framework are the estimation of Group-1 bubble size and the amount of void in the liquid slug, which is a function of Group-1 void fraction. Hibiki and Ishii’s (2002) correlation is utilized to predict the size of the Group-1 bubbles. A correlation is developed to estimate the Group-1 void fraction. The developed model for the estimation of interfacial area concentration is compared with the three existing datasets. These are data for air–water flow taken in annular geometry and round tube and also for air–NaOH solution taken in round tube. The estimation accuracies for these data sets are ±36.4%, ±26.5% and ±37.4%, respectively. These datasets cover a wide range of flow regimes and different physical properties. [Copyright &y& Elsevier]

Abstract: Ionic liquids (ILs) have been widely considered as potential green solvents for CO2 capture, and many promising ionic liquids have been synthesized and reported. However, knowledge related to the hydrodynamics of CO2 absorption with ionic liquids especially the bubble behavior is still scarce compared with the conventional molecular solvents. In this study, it is the first time to discuss the multi-bubble behavior in a carbon capture system with ionic liquid by using a high speed image pick-up system. The bubble behavior, such as bubble size distribution, total gas holdup, Sauter diameter and interfacial area at different operating conditions are investigated. The experimental results show that the bubble diameter of CO2–[bmim][BF4] system is smaller than that of N2–[bmim][BF4] system. The bubble diameter increases as the gas superficial velocity increases and the height along the axis of the column rises, but decreases with the increase of the temperature. The total gas holdup in [bmim][BF4] increases with the increase of the system temperature due to the decrease of the ionic liquid viscosity. In addition, the gas superficial velocity improves the total gas holdup due to the higher gas momentum favors the formation of small bubbles. A new correlation based on the experimental data is proposed for the prediction of Sauter diameter in gas–ionic liquid systems. The prediction results calculated by the new correlation are in good agreement with the experimental data with a relative error less than 6%. [Copyright &y& Elsevier]

Precipitation of naphthenate salts is normally a problem in the processing of acidic crude oils. In this study, the goal was to find suitable methods to investigate the interfacial reaction between tetraacid and calcium under emulsified conditions. Two different systems have been studied depending on composition and applied shear. The influence of inhibitors has been investigated and the same inhibitor was found to be the most effective one regardless of the system. Depletion of tetraacid in the oil phase was analyzed with UV-vis and HPLC. Interfacial area and droplet size in the emulsions were measured with fluorescence microscope and pulse-field gradient NMR. Since this reaction takes place over the interface, the investigation clearly documents, the importance of the total interfacial area of the emulsified system. [ABSTRACT FROM AUTHOR]

Abstract: Current thermal–hydraulic analysis codes use static, flow-regime-dependent empirical models which introduce several sources of error and numerical instability. The interfacial area transport equation offers a more robust, reliable prediction of interfacial area and can allow for dynamic predictions of two-phase flows. In order to develop reliable mechanistic models for interfacial area concentration sources and sinks an extensive database is required, however the current database lacks significant data for pipes larger than 0.1m diameter and for void fractions above 0.4. To improve and extend the database experiments have been performed in pipes with diameters of 0.152m and 0.203m with void fractions of up to 0.7, providing valuable data regarding the local profiles and axial development that can be used to evaluate current interfacial area transport models and assist in the development of new mechanistic models for interfacial area concentration sources and sinks. [Copyright &y& Elsevier]

The capillary pressure-saturation ( P- S) relationship is one of the central constitutive relationships used in two-phase flow simulations. There are two major concerns regarding this relation. These concerns are partially studied in a hypothetical porous medium using a dynamic pore-network model called DYPOSIT, which has been employed and extended for this study: (a) P- S relationship is measured empirically under equilibrium conditions. It is then used in Darcy-based simulations for all dynamic conditions. This is only valid if there is a guarantee that this relationship is unique for a given flow process (drainage or imbibition) independent of dynamic conditions; (b) It is also known that P- S relationship is flow process dependent. Depending on drainage and imbibition, different curves can be achieved, which are referred to as 'hysteresis'. A thermodynamically derived theory (Hassanizadeh and Gray, Water Resour Res 29: 3389-3904, ) suggests that, by introducing a new state variable, called the specific interfacial area ( a, defined as the ratio of fluid-fluid interfacial area to the total volume of the domain), it is possible to define a unique relation between capillary pressure, saturation, and interfacial area. This study investigates these two aspects of capillary pressure-saturation relationship using a dynamic pore-network model. The simulation results imply that P- S relation not only depends on flow process (drainage and imbibition) but also on dynamic conditions for a given flow process. Moreover, this study attempts to obtain the first preliminary insights into the global functionality of capillary pressure-saturation-interfacial area relationship under equilibrium and non-equilibrium conditions and the uniqueness of P- S- a relationship. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical behavior of carbon xerogels was studied with the aim of analyzing the performance of the materials used as electrochemical supercapacitors (SC) and to relate with physicochemical parameters. These materials have areas involving 1500–2000 m2/g measured with the BET equation and a range of pore size distributions. Conventional electrochemical techniques were used as cyclic voltammetry (CV), which allowed electrochemical characterization of different materials, and chronopotentiometry (CD), in order to determine the charge storage capacity of the xerogel at different currents or discharge rates. Experimental results using electrochemical impedance spectroscopy (EIS) were interpreted with a physicochemical model that permitted identifying different parameters of the electrode, which explain the differences in the behavior of materials. [Copyright &y& Elsevier]

Abstract: The emission of CO2 into the atmosphere is causing majority of the global warming and thus various end-of-pipe treatment methods have evolved to capture CO2 from fixed point sources. The present article deals with CO2 capture from a simulated gas stream using dilute NaOH solution in a spray column using a two-phase critical flow atomizer capable of producing very fine sprays with high degree of uniformity and moving at very high velocities. Experimentation was carried out to investigate the percentage removal of CO2 as well as interfacial area as functions of different variables. The maximum percentage removal of CO2 observed was about 99.96% for a Q L/Q G ratio of 6.0m3/1000ACM (liquid flow rate of 1.83×10−5 m3/s and gas flow rate of 3.33×10−3 m3/s) and for a CO2 feed rate of 100l/h, while the observed values of interfacial area were in the range of 22.62–88.35m2/m3 within the framework of the experimentation. A simple correlation was developed for predicting the interfacial area as functions of various pertinent variables of the system. Experimental data fitted excellently well with the correlation. The comparison of the interfacial area observed between the present system and the existing systems revealed that the present system produced higher values of interfacial area than the existing systems and hence the performance of the system was better than the existing system. [Copyright &y& Elsevier]

In this study, simultaneous measurement of interfacial area distribution and mass transfer coefficients in a bubble column for two-phase dispersed system of air-water is conducted. The time-averaged interfacial area (a) distribution was measured by using ultrasonic computed tomography (UCT), the volumetric liquid mass transfer coefficient (kLa) is measured by dynamic method, and hence, the liquid side mass transfer coefficient (kL) and a. The UCT results show that the higher interfacial area around the center of the column and the lower one near the column wall. The experimental results of interfacial area are in a good agreement with the results obtained by the reported correlation and the results obtained by the physical method. A good agreement is also obtained between the experimental results of liquid side mass transfer coefficient and those by the reported correlation. [ABSTRACT FROM AUTHOR]

Abstract: The efficacy of power ultrasound of 20kHz in enhancing the volumetric mass transfer coefficient was investigated in this study. Breakage and dissolution of sparingly soluble benzoic acid dispersed in either water or 24% aqueous glycerol was monitored as a function of time and ultrasound power input. Particle size measurements were carried out at intermediate times during the experiment to estimate the mean particle size and surface area. Linear combination of lognormal distributions was found to fit the experimental particle size distribution data. The De Brouckere mean diameters (d 43) obtained from the particle size distributions decreased with increase in the ultrasonic power level. Empirical correlations were developed for the evolution of surface area as a function of ultrasonic energy input per unit mass. The effect of ultrasound on the intrinsic mass transfer coefficient (k c) could be decoupled from the volumetric mass transfer coefficient (k c a) as the surface area was also estimated. Different approaches involving either constant or variable intrinsic mass transfer coefficients were employed when carrying out the delineation. Mass transfer rates were enhanced due to both higher ultrasound induced intrinsic convective mass transfer coefficient and additional surface area created from particle breakage. To delineate the effects of particle breakage from solid dissolution, experiments were also carried out under non-mass transfer conditions by pre-saturating the solvents with benzoic acid. Both the solid–liquid systems examined in the present study attained saturation concentration when the ultrasonic energy input per unit mass was approximately 60kJ/kg, irrespective of the ultrasonic power level setting. [Copyright &y& Elsevier]

Abstract: The mechanisms that govern the transport of colloids in the unsaturated zone of soils are still poorly understood, because of the complexity of processes that occur at pore scale. These mechanisms are of specific interest in quantifying water quality with respect to pathogen transport (e.g. Escherichia coli, Cryptosporidium) between the source (e.g. farms) and human users. Besides straining in pore throats and constrictions of smaller or equivalent size, the colloids can be retained at the interfaces between air, water, and grains. Theories competing to explain this mechanism claim that retention can be caused by adhesion at the air–water-interface (AWI) between sediment grains or by straining at the air–water–solid (AWS) contact line. Currently, there are no established methods for the estimation of pathogen retention in unsaturated media because of the intricate influence of AWI and AWS on transport and retention. What is known is that the geometric configuration and connectivity of the aqueous phase is an important factor in unsaturated transport. In this work we develop a computational method based on level set functions to identify and quantify the AWS contact line (in general the non-wetting–wetting–solid contact line) in any porous material. This is the first comprehensive report on contact line measurement for fluid configurations from both level-set method based fluid displacement simulation and imaged experiments. The method is applicable to any type of porous system, as long as the detailed pore scale geometry is available. We calculated the contact line length in model sediments (packs of spheres) as well as in real porous media, whose geometry is taken from high-resolution images of glass bead packs and sedimentary rocks. We observed a strong dependence of contact line length on the geometry of the sediment grains and the arrangement of the air and water phases. These measurements can help determine the relative contribution of the AWS line to pathogen retention. [Copyright &y& Elsevier]

Abstract: Flow in large pipes is important in a wide variety of applications. In the nuclear industry in particular, understanding of flow in large diameter pipes is essential in predicting the behavior of reactor systems. This is especially true of natural circulation Boiling Water Reactor (BWR) designs, where a large-diameter chimney above the core provides the gravity head to drive circulation of the coolant through the reactor. The behavior of such reactors during transients and during normal operation will be predicted using advanced thermal–hydraulics analysis codes utilizing the two-fluid model. Essential to accurate two-fluid model calculations is reliable and accurate computation of the interfacial transfer terms. These interfacial transfer terms can be expressed as the product of one term describing the potential driving the transfer and a second term describing the available surface area for transfer, or interfacial area concentration. Currently, the interfacial area is predicted using flow regime dependent empirical correlations; however the interfacial area concentration is best computed through the use of the one-dimensional interfacial area transport equation (IATE). To facilitate the development of IATE source and sink term models in large-diameter pipes a fundamental understanding of the structure of the two-phase flow is essential. This understanding is improved through measurement of the local void fraction, interfacial area concentration and gas velocity profiles in pipes with diameters of 0.102m and 0.152m under a wide variety of flow conditions. Additionally, flow regime identification has been performed to evaluate the existing flow regime transition criteria for large pipes. This has provided a more extensive database for the development and evaluation of IATE source and sink models. The data shows the expected trends with some distortion in the transition region between cap-bubbly and churn-turbulent flow. The flow regime map for the 0.102m and 0.152m diameter test sections agree with the existing flow regime transition criteria. It may be necessary to perform further experiments in larger pipes and at higher gas flow rates to expand the range of conditions for which models can be developed and tested. [Copyright &y& Elsevier]

Abstract: The interfacial area in the Taylor (slug) gas–liquid flow in a microchannel was measured by the Danckwerts'' (chemical) method, using CO2 absorption from the CO2/N2 mixture into KHCO3/K2CO3 buffer solutions, containing NaOCl as a catalyst. The rate of absorption was determined and the Danckwerts'' plots were constructed. Reasonable agreement with the geometrical area measured photographically was obtained. This fact allowed to determine for the first time the mass transfer coefficients separately for liquid film and liquid caps. A correlation for the calculation of mass transfer coefficients has been proposed. [Copyright &y& Elsevier]

Abstract: Prototype of structured microreactor plates with 300μm deep flow channels was developed. Two plates with different structural elements, square and triangular, were used in the study. Flow behavior was investigated and the results showed excellent mixing behavior of gas and liquid phases. Hydrodynamic parameters and volumetric gas–liquid mass transfer coefficients were determined at various flow conditions. Gas holdup and the gas–liquid interfacial area were determined by an optical method using image processing software. Volumetric mass transfer coefficients were measured using nitrogen to strip oxygen from deionized water. The experimental results indicate a high mass transfer rate. Gas holdup and the total gas–liquid interfacial area were in the range of 20–45% and 2600–5600m2 m−3, respectively. Volumetric mass transfer coefficients were as high as 1.1s−1. An empirical correlation for the mass transfer coefficient was derived. [Copyright &y& Elsevier]

Abstract: Absorption process in amine solutions has been identified as the best available technology for post combustion CO2 capture among the available technologies for controlling CO2 release. In this work, a video technique combined with image processing was used to measure gas hold-up, bubble diameter and gas–liquid interfacial area in three sections of a bubble column. The evolution of these parameters as a function of height in the column has been investigated. CO2–alkanolamine systems (MEA and MDEA) were studied at different amine concentrations (from 0 to 1M) and gas flow rate (10–25L/h). New data on gas hold-up, Sauter diameter and interfacial area are presented. The experimental measurements showed that amine concentration and gas flow rate have a great influence on interfacial area. Moreover, it was proposed an empirical equation to relate the interfacial area to time and the height in the column for each system. [Copyright &y& Elsevier]

Abstract: Production of biodiesel from rice bran and karanja oils was studied in a stirred tank reactor at different agitator speeds. The reaction system involves two immiscible phases: oil and methanol. The minimum critical speed and the emulsion properties for the reacting system were measured. Based on these values the sauter mean diameter, interfacial area and flow regime were obtained. The minimum critical speed of agitator for rice bran was 700–750rpm and for karanja was 550–650rpm. The lower rpm for karanja oil is due to the presence of gums in the non-edible oils. The flow regime for the non-reacting system was found to be transitional and turbulent for reacting. The sauter mean diameter decreased to 7–8 times, from 2010 to 240μm with increased agitator speed in the initial stages of the reaction and then was found to be constant with further increase. The specific interfacial area obtained from sauter mean diameter showed an increase accordingly. The economics of the biodiesel process depends on the conversions which also dictate the yield. The characteristics determined in the present work are useful in understanding the biodiesel process and help in the scale up of the reactor using different feed-stocks. [Copyright &y& Elsevier]

Abstract: Inverted organic photovoltaic devices with a structure of fluorine tin oxide (FTO)/ZnO/poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C61 butyric acid methyl ester (PCBM)/Ag were fabricated, in which ZnO interlayer serves as an electron selective layer. The ZnO interlayer includes three different nanostructures: polycrystalline seed layer, polycrystalline seed layer/loose nanopillars and polycrystalline seed layer/dense nanopillars. The influences of the different ZnO interlayers on the device performance were investigated. It is concluded that the polycrystalline seed layer/loose nanopillars offer more interfacial area with the P3HT:PCBM blends and acts as a continuous conducting path to the cathode. Our results demonstrate that effective infiltration of the blends into the ZnO nanopillars is critical for optimizing the device performance. [Copyright &y& Elsevier]

Abstract: This study investigates the pressure drop characteristics, shear stress in packed bed with shear thinning power law type non-Newtonian liquid. A mechanistic model has also been developed to analyze the pressure drop and interfacial stress in packed bed with non-Newtonian liquid by considering the loss of energy due to wettability. The Ergun''s and Foscolo''s equations were used for comparison with the experimental data. The Ergun equation was modified to account for the effect of flow behavior index of non-Newtonian fluid in the column. The intensity factor of shear stress and the friction factor were analyzed based on energy loss due to wettability effect of liquid on the solid surface. [Copyright &y& Elsevier]

Abstract: The present work analyses the hydrodynamic behaviour of a gas phase in a bubble column using different emulsions as liquid phase. The hydrodynamic behaviour was analysed on the basis of gas hold-up, bubble diameter and gas–liquid interfacial area; the different variables employed in this study [gas flow-rate (between 18 and 40Lh−1), as well as the organic phase nature, the organic phase concentration (between 0 and 1% (vol)) and the surfactant presence (between 0 and 0.1% (vol))] have been taken into account. The results obtained have been explained on the basis of the liquid phase physical properties and the special characteristics of the gas–liquid–liquid systems. [Copyright &y& Elsevier]

Abstract: This work focused on lipase-catalyzed triglyceride hydrolysis in biphasic media. The effect of specific interfacial area of oil-in-water emulsions on the hydrolysis activity of lipase was particularly investigated following a rigorous methodology and using two different oils, tributyrin and olive oil. The specific interfacial area was varied over several orders of magnitude by changing either the amount of emulsified oil or the average diameter of oil droplets. This work particularly focused on the effect of changing droplet size (at given amount of oil) on lipase activity. When the specific interfacial area was varied over several orders of magnitude, the specific activity of the enzyme exhibited a non-monotonic variation with a pronounced maximum. At low specific interfacial area, initial velocity increased with specific interfacial area. Inhibition of enzyme activity at a high interfacial concentration of triglyceride was observed. Experimental results were interpreted on the basis of a theoretical mechanism assuming Michaelis–Menten mechanism for enzyme catalysis, Langmuir-type adsorption isotherm for enzyme and limitation of enzyme–substrate formation by enzyme adsorption process. [Copyright &y& Elsevier]

The objective of this study is to obtain quantitative evidence of pore-scale immiscible fluid distribution in oil-wet and water-wet porous media using X-ray computed microtomography. Temporal and spatial saturation profiles, as well as surface and interfacial areas, are thoroughly analyzed through cycles of drainage and imbibition using samples with different wetting characteristics but similar pore structures. The population of individual immiscible fluid structures ('blobs') was also evaluated. The specific nonwetting phase surface areas of both porous media are found to be in close correlation with the specific solid surface area. On the other hand, the differing wetting strengths of the two porous media affect the curvature of the fluid-fluid interface and thus the specific meniscus interfacial area of the two porous media. Although the magnitude of the specific meniscus interfacial areas is different, they both trend toward a maximum at wetting phase saturations of 0.35-0.55. The differences in wetting characteristics are also apparent in the blob populations. The number of blobs in the oil-wet porous media is three times greater than that of the water-wet porous media at similar saturations; the increase in population is a result of the increase in the amount of smaller blobs inhabiting the smaller pore spaces. The surface areas of individual blobs as a function of the individual blob volumes are found to closely agree with the specific surface area of a sphere at blob volumes below the minimum individual grain volume and with the specific pore space surface area above this volume. These results show how wettability and saturation history influence the distribution of immiscible fluids within the pore space. [ABSTRACT FROM AUTHOR]

Classical Darcy's equation for multiphase flow assumes that gravity and the gradient in fluid pressure are the only driving forces and resistance to the flow is parameterized by (relative) permeability as a function of saturation. It is conceivable that, in multiphase flow, other driving forces may also exist. This would mean that such nonequilibrium effects are lumped into a permeability coefficient. Indeed, many studies have shown that the relative permeability coefficient generally depends not only on saturation but also on dynamics of the system. Through the application of rational thermodynamics, a theory of two-phase flow had been developed in which interfacial areas were introduced as separate thermodynamic entities and their macroscale effects were explicitly included. This theory includes new driving forces whose significance needs still to be established. To study new terms in the theory, we employ a dynamic pore network model called DYPOSIT. A long pore network (several representative elementary volumes connected in series) is generated, which represents as a one-dimensional porous medium column. This model provides pore scale distribution of local phase pressures, capillary pressure, interfacial area, saturation, and flow rate, which are averaged to obtain the macroscale distributions of these variables. Our analysis shows that there are discrepancies between the simulation results and the classical equations to describe the transient behavior, especially for the nonwetting phase transient permeability. The coefficients in the extended equations are quantified and parameterized. Although under the applied Dirichlet boundary conditions, flow varies significantly, there is a clear trend illustrating dependency of coefficients on saturation, independent of dynamic conditions. Furthermore, using the new coefficients, it is possible to explain either transient or steady state flow regimes, which is a new achievement. [ABSTRACT FROM AUTHOR]

The extended Darcy's law is a commonly used equation for the description of immiscible two-phase flow in porous media. It dates back to the 1940s and is essentially an empirical relationship. According to the extended Darcy's law, pressure gradient and gravity are the only driving forces for the flow of each fluid. Within the last two decades, more advanced and physically based descriptions for multiphase flow in porous media have been developed. In this work, the extended Darcy's law is compared to a thermodynamically consistent approach which explicitly takes the important role of phase interfaces into account, both as entities and as parameters. In this theoretically derived approach, forces related to capillarity and interfaces appear as driving/resisting forces, in addition to the traditional terms. It turns out that the extended Darcy's law and the thermodynamically based approach are compatible if either (i) relative permeabilities are a function of saturation only, but capillary pressure is a function of saturation and specific interfacial area or (ii) relative permeabilities are a function of saturation and saturation gradients. Theoretical considerations suggest that the former alternative is only valid in case of reversible displacement while in the general case (irreversible displacement), the latter alternative is relevant. [ABSTRACT FROM AUTHOR]

Abstract: In this work the simulation of a wet flue gas desulfurization (FGD) unit with spray tower of a power plant is presented, aiming at an efficient follow-up and the optimization of the FGD system operation. The dynamic model developed to simulate the performance of the system has been validated with operation data collected over a long period of time. All the partaking physical and chemical processes like the limestone dissolution, the crystallization of calcium sulfite and gypsum and the oxidation of sulfite ions have been taken into account for the development of the simulation model while the gas absorption by the liquid droplets was based on the two-film theory. The effect of the mean diameter of the slurry droplets on the performance of the system was examined, as it was used as an index factor of the normal operation of the system. The operation limits of the system were investigated on the basis of the model developed. It is concluded that the model is capable of simulating the system for significantly different SO2 loads and that the absorption rate of SO2 is strongly affected by the liquid dispersion in the tower. [ABSTRACT FROM AUTHOR]

Abstract: This work is the eighth in a series that develops the fundamental aspects of the thermodynamically constrained averaging theory (TCAT) that allows for a systematic increase in the scale at which multiphase transport phenomena are modeled in porous medium systems. In these systems, the explicit locations of interfaces between phases and common curves, where three or more interfaces meet, are not considered at scales above the microscale. Rather, the densities of these quantities arise as areas per volume or length per volume. Modeling of the dynamics of these measures is an important challenge for robust models of flow and transport phenomena in porous medium systems, as the extent of these regions can have important implications for mass, momentum, and energy transport between and among phases, and formulation of a capillary pressure relation with minimal hysteresis. These densities do not exist at the microscale, where the interfaces and common curves correspond to particular locations. Therefore, it is necessary for a well-developed macroscale theory to provide evolution equations that describe the dynamics of interface and common curve densities. Here we point out the challenges and pitfalls in producing such evolution equations, develop a set of such equations based on averaging theorems, and identify the terms that require particular attention in experimental and computational efforts to parameterize the equations. We use the evolution equations developed to specify a closed two-fluid-phase flow model. [ABSTRACT FROM AUTHOR]

Abstract: Effects of different T-junction injectors on the generation of a N2–water Taylor flow has been investigated experimentally in a channel of 300μm by 300μm. 4 different inlet geometries and 2 feeding configurations are evaluated in a wide range of fluid flow rates ratio 0< Q G/Q L <35. It has been demonstrated that for a given flow rate ratio different patterns of the unit cell (1bubble+1 slug) can be formed showing the impact of inlet geometries. An attempt to rationalize the result is proposed using a Garstecki-type scaling law for bubble length prediction. A unique geometrically based scaling law is discussed and a quite good agreement is obtained to describe the whole set of experiments, provided that there is no bubble coalescence: Finally an analysis in terms of specific interfacial area location (caps or bubble body) is proposed showing the interest of such inlet geometries to tune this parameter for fixed fluid flow rates and opening new possibilities for local mass transfer studies in the G–L Taylor flow configuration in square micro-channels. [Copyright &y& Elsevier]

Abstract: In this study, we investigated the kinetics of linoleic acid production via lipase-mediated hydrolysis of corn DDGS oil in a batch reactor with continuous mechanical agitation and developed a kinetic model that incorporated the product inhibition to study the complete hydrolysis. The model agreed very well with observed data; though situations with low enzyme dosage or low stirring rates were modeled successfully without product inhibition, actual product concentration in such situations was too low to exert any inhibitory effects. Increasing the enzyme concentration increased hydrolysis, and beyond certain enzyme concentrations, effects tended to fade away because of excessive enzyme desorption from the interface. An enzyme dosage within the range of 40–60KLU/L of oil dispersion could be successfully applied for a substrate concentration of 25–50g/L of DDGS oil. Increasing the agitation rates improved enzymatic hydrolysis, but a higher stirring rate of 1000rpm moderately improved production of linoleic acid compared with a stirring rate of 750rpm. Within the range of substrate concentrations studied, enzymatic inhibition was moderate but still evident. The high degree of hydrolysis (i.e., ∼96% of theoretical linoleic acid yield) from DDGS oil suggests this method has potential for commercial production of linoleic acid. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the pressure drop (Δp) generated by a static mixer with sieve plates in two-phase downflow (water as a continuous phase), and the mass transfer efficiency (kLa, a) with the performance of other static mixers (Sulzer, Kenics, Karman, etc.). The relationships for Δp, kLa and interfacial area (a) calculation depending on liquid and gas phase velocities and geometry of the plates (sieves) in this static mixer are presented. kLa was found to be strictly proportional to the power consumption (P/V) and its values were quite close to those obtained in Sulzer & Kenics mixers with an 8-element mesh. Enhancement factors for oxygen absorption in the sodium sulphite solution and for ozone absorption in Lake Ulemiste water were calculated and the plausible values of the interfacial area (a) were estimated. [ABSTRACT FROM AUTHOR]

Abstract: Free enzyme lipolase 100T from Thermomyces lanuginosus has been investigated as a hydrolyzing catalyst in a spray extraction column. The aqueous buffer (pH 7.0) enzyme solution as continuous phase (batch-wise) and the oil as dispersed phase have been used. Various operating parameters which affect the drop size in a spray column, i.e. nozzle diameter, oil flow rate, etc. have been studied. Using the optimized flow rate and nozzle diameter, the effect of various other operating parameters such as concentration of enzyme, enzyme solution height (oil residence time) on the hydrolysis reaction has been evaluated. The highest conversion is obtained for the optimum flow rate of 3.8ml/min and the nozzle diameter of 0.75mm. The experimental result showed that the extent of hydrolysis of castor oil is 0.16% in a column reactor due to drop coalescing is almost equal to the hydrolysis due to drop residence time of 1min in the column. It was also observed that the enzyme activity does not show any appreciable change up to a maximum of 44 passes in the spray column. The contributions of various hydrodynamic phenomena, such as drop formation, rise and coalesce of drops, to the overall hydrolysis rate have been estimated and discussed. Experimental data obtained for the spray column have been compared with that of an agitated batch reactor. [ABSTRACT FROM AUTHOR]

Abstract: The concept of the wire bundle packing is regarded as a potential alternative to common structured packings in the chemical industry, but until now it is still in prototype stadium and its capability has to be proven. The packing mainly consists of parallel vertical wires that are supplied with liquid separately from a special liquid distributor. To gain insight into the fluid dynamics of the gas/liquid flow, experiments with a single wire in a channel are conducted. Different methods are employed to measure local film thicknesses, liquid hold-up, liquid bead velocities, load limits and pressure drop. Due to the strongly curved surface of the wire, the film flow differs from the fluid dynamics of liquid films on plane surfaces. The film flow shows a distinctive pattern of liquid “beads” that run on a thin basis film. When the film is subject to a significant counter current gas flow the flow pattern changes, but the liquid hold-up and the interfacial area are hardly influenced. This behaviour can be observed up to the load limit where the beads disintegrate and flooding occurs. An estimation of the fluid dynamic performance of the wire packing from the single wire experimental data is made. The results indicate that the interfacial area of the fully wetted packing exceeds the dry packing area up to 60%. The estimated pressure drop is about one magnitude lower than that of a comparable corrugated sheet structured packing and the load limits are significantly higher. [ABSTRACT FROM AUTHOR]

Abstract: Gas holdup, bubble diameter and gas–liquid interfacial area were measured in a bubble column, during the absorption of CO2 in DEA solutions in batch conditions, as a function of column height, operating time, gas flow rate and amine concentration. The experimental measurements of bubble diameter were carried out using a video technique combined with image processing. The gas flow rate was varied in the range 10–25L/h, and the amine concentration between 0.05 and 1M. The results show that the interfacial area is influenced with the amine concentration and gas flow rate through the column. Additionally, an empirical equation is proposed to relate the interfacial area to time and column height for each system. Furthermore, a generalized correlation based on dimensionless groups for the prediction of gas holdup in homogeneous regime was proposed and found to be in good agreement with available data. [Copyright &y& Elsevier]

Abstract: MnO2 nanostructures are successfully coated onto activated mesocarbon microbeads (a-MCMB) by a simple chemical coprecipitation method. The structure and morphology of the as-prepared a-MCMB/MnO2 composite were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the nano-MnO2 is of short fiber-like structures with about 200nm in length and 60nm in width. A growing mechanism was also proposed for the nano-MnO2 on the surface of a-MCMB. This novel composite was used as an electrode material for supercapacitors. Electrochemical measurements showed that the composite electrode has a maximum specific capacitance of 183Fg−1 in 1M LiPF6 (EC+DMC) organic electrolyte with an operating voltage up to 3.0V. The specific capacitance base on the MnO2 is estimated to be as high as 475Fg−1, corresponding to a considerable energy density of 106whkg−1. [Copyright &y& Elsevier]

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In this work, the constitutive relationship between capillary pressure ( P c), saturation ( S w), and fluid-fluid interfacial area per volume (IFA) is characterized using computed microtomography for drainage and imbibition experiments consisting of a nonaqueous phase liquid and water. The experimentally measured relationship was compared to a thermodynamic model that relates the area under the P c − S w curve to the total IFA, a n, and the capillary-associated IFA, a nw. Surfaces were fit to the experimental and modeled P c − S w − a n and P c − S w − a nw data in order to characterize the relationship in three dimensions (3D). For the experimental system, it was shown that the P c − S w − a n relationship does not exhibit hysteresis. The model is found to provide a reasonable approximation of the magnitude of the 3D surfaces for a n and a nw, with a mean absolute percent error of 26% and 15%, respectively. The relatively high mean absolute percent errors are primarily the result of discrepancies observed at the wetting- and nonwetting-phase residual saturation values. Differences in the shapes of the surfaces are noted, particularly in the curvature (arising from the addition of scanning curves and presence of a n − S w hysteresis in the predicted results) and endpoints (particularly the inherent nature of thermodynamic models to predict significant a nw associated with residual nonwetting-phase saturation). Overall, the thermodynamic model is shown to be a practical, inexpensive tool for predicting the P c − S w − a n and P c − S w − a nw surfaces from P c − S w data. [ABSTRACT FROM AUTHOR]

Abstract: Gas holdup, bubble behavior, interfacial area and gas–liquid mass transfer in a 5m internal-loop airlift reactor with non-Newtonian fluid were studied in the superficial gas velocity (U g) range of 2–12cm/s. Air and aqueous CMC solutions of 0–0.45wt% were used as the gas and liquid phases, respectively. It was found that increased U g or CMC concentration led to a wider bubble size distribution and an increase in the bubble Sauter diameter. The volumetric mass transfer coefficient increased with an increase in U g and a decrease in CMC concentration. In the air–water system, k l a/α g was found to be independent of U g and was 0.21/s, and a constant liquid-side mass transfer coefficient (k l) was found in the heterogeneous regime. However, in the air–CMC solution system, the influences of the superficial gas velocity and liquid viscosity were much more complicated: k l a/α g was not constant and was affected by the superficial gas velocity and CMC concentrations; the interfacial area increased with an increase in U g and a decrease in CMC concentration; k l increased more significantly with increasing U g, and no obvious trend was found for the influence of CMC concentration on k l. [Copyright &y& Elsevier]