Multiphase Behavior Research Articles

Computational fluid dynamics study of the parameters affecting oil—water hydrocyclone performance

Parameters affecting the performance of de-oiling hydrocyclones are related to geometry, flow, and the fluids to separate. Global assessment studies have been conducted since the invention of the device in the 1980s, while the internal flow field still deserves exploration. The present work investigates the multi-phase flow behaviour of a de-oiling hydrocyclone using computational fluid dynamics. The Reynolds stress and the renormalization group k—ε turbulence models combined with the multi-phase mixture model, implemented in the commercial code FLUENT, were employed to predict the different features of the complex multi-component flow inside the hydrocyclone. Profiles of the velocity components and the Reynolds stresses revealed interesting explanations of the effects of feed flowrate, feed oil concentration, and oil droplet size on the separation efficiency, which is the most important performance indicator. Pressure drop and friction coefficient results are also presented and discussed.

Hyperthermostable acetyl xylan esterase

SummaryAn esterase which is encoded within a Thermotoga maritima chromosomal gene cluster for xylan degradation and utilization was characterized after heterologous expression of the corresponding gene in Escherichia coli and purification of the enzyme. The enzyme, designated AxeA, shares amino acid sequence similarity and its broad substrate specificity with the acetyl xylan esterase from Bacillus pumilus, the cephalosporin C deacetylase from Bacillus subtilis, and other (putative) esterases, allowing its classification as a member of carbohydrate esterase family 7. The recombinant enzyme displayed activity with p‐nitrophenyl‐acetate as well as with various acetylated sugar substrates such as glucose penta‐acetate, acetylated oat spelts xylan and DMSO (dimethyl sulfoxide)‐extracted beechwood xylan, and with cephalosporin C. Thermotoga maritimaAxeA represents the most thermostable acetyl xylan esterase known to date. In a 10 min assay at its optimum pH of 6.5 the enzyme's activity peaked at 90°C. The inactivation half‐life of AxeA at a protein concentration of 0.3 µg µl−1 in the absence of substrate was about 13 h at 98°C and about 67 h at 90°C. Differential scanning calorimetry analysis of the thermal stability of AxeA corroborated its extreme heat resistance. A multi‐phasic unfolding behaviour was found, with two apparent exothermic peaks at approximately 100–104°C and 107.5°C. In accordance with the crystal structure, gel filtration analysis at ambient temperature revealed that the enzyme has as a homohexameric oligomerization state, but a dimeric form was also found.

Modeling of the Multiphase Behavior of Nitrogen-Containing Systems at Low Temperatures with Equations of State

In this work, we present the modeling of the vapor−liquid−liquid equilibria (VLLE) for three ternary systems that are of interest in the natural gas and oil industry: nitrogen + methane + n-pentane, nitrogen + methane + n-hexane, and nitrogen + methane + n-heptane. The capabilities of the PC-SAFT and SRK equations of state to predict the complex phase behavior exhibited at low temperatures by the systems studied were compared and analyzed. The computer algorithm performing the isothermal multiphase flash calculations in the first case is based on the minimization of the Gibbs energy, while the second is based on the minimization of a modified tangent−plane distance function. The results obtained demonstrate that both equations of state predict with reasonable accuracy the experimentally observed phase behavior of the ternary systems considered.

Multimorphism in molecular monolayers: Pentacene on Cu(110)

The architecture of the contacting interface between organic molecular semiconductors and metallic or insulating substrates determines its cooperative properties such as the charge injection and the charge-carrier mobility of organic thin-film devices. This paper contributes a systematic approach to reveal the evolution of the different structural phases of pentacene on Cu(110) while using the same growth conditions. Complementary measurement techniques such as scanning tunneling microscopy and low-energy electron diffraction together with ab initio calculations are applied to reveal the complex multiphase behavior of this system at room temperature. For coverages between 0.2 and 1 monolayer (ML) a complex multiphase behavior comprising five different phases is observed, which is associated to the interplay of molecule/molecule and molecule/substrate interactions. Multimorphism critically depends on the thermodynamics and kinetics determined by the growth parameters as well as the system itself and arises from shallow energy minima for structural rearrangements. In consequence, the multimorphism affects the interface structure and therefore the interface properties.

Tie-simplex based mathematical framework for thermodynamical equilibrium computation of mixtures with an arbitrary number of phases

We present a general framework for the computation of the thermodynamic behavior of multi-phase, multi-component systems. In this framework we use the fact that for given values of pressure and temperature the compositional space can be represented as a high dimensional simplex, while the phase equilibrium conditions can be represented by a low dimensional tie-simplex. We parameterize the high dimensional compositional space using a lower dimensional tie-simplex subspace. The tie-simplex computation and interpolation procedures complement the parameterization and complete the mathematical framework. We demonstrate that the tie-simplex space fully describes the solution route for displacements involving multi-phase mixtures. The efficiency of the method is demonstrated for several multi-phase equilibrium problems of practical interest. The tie-simplex parameterization can be performed in a preprocessing step to replace the flash computations completely, or can be used as an initial guess to accelerate the convergence of standard procedures. For general-purpose flow simulation, adaptive construction of the necessary tie-simplexes during the course of a simulation is an efficient strategy.

Influence of Nanoroughness and Detailed Surface Morphology on Structural Properties and Water-Coupling Capabilities of Surface-Bound Fibrinogen Films

Adsorption of fibrinogen onto nanorough platinum surfaces was investigated using radiolabeling and quartz crystal microbalance with dissipation (QCM-D). In total, four surface topographies were studied with a root-mean-square (rms) roughness value ranging from 1.49 to 9.01 nm, including one surface with sharp whiskerlike surface protrusions and three surfaces with more smoothly shaped surface features. From the radiolabeling results, it is concluded that the fibrinogen adsorption process is influenced by surface roughness, and by combining radiolabeling with QCM-D, we found that the water content of the fibrinogen layers formed on respective surfaces depends significantly on the detailed surface morphology in question. Furthermore, from plots of the dissipation versus frequency shift obtained with QCM-D, the presence of several distinct adsorption phases on nanorough surfaces with more smoothly shaped surface features was observed. This type of multiphased adsorption behavior was not observed on flat refe...

“Wellbore Integrity...” Say What??

Convincing people to try something new, strange and expensive is not easy. Convincing them to embrace something that they fear and struggle to understand is almost impossible. Many people seem to fear CO2 Capture and Storage (CCS) and remain skeptical that it will evolve into a huge opportunity to control global CO2 emissions. It needs to be explained in terms normal people understand. Not everyone speaks the same language or starts from the same point of reference. This effort is by a high school junior using common language and images familiar to me and my friends to visualize basic science relationships related to the storage part of CCS: soccer balls and playing fields. It considers key components of well systems and makes comparisons with the behavior of natural phenomena like ant hills enduring in a light rain storm, and compares that with their fate when attacked by a little brother with a water hose. It asks questions about the dimensions of the systems, and how key components might work. It’s about putting CO2 underground, but how do you explain that with soccer balls? Instinctively, the big question is will the CO2 stay underground? What will happen to it with time? Why won’t it just come right back out a well like a straw? What about all those wells anyway? Should people get hyped-up about them? Aren’t they filled with cement? Think, CO2 in water makes an acid. What will that acid do? Is it about pumping and sucking fluids thru barriers as strong as steel instead of allowing them to flow freely in a hose? Stay tuned and read on. Full disclosure: This paper is not exactly cutting edge science; it offers no new data, and tests no hypothesis although it makes some original calculations. It’s about communication and visualization, so it deliberately dodges some important details about well construction techniques, reaction rates, kinetics and the multiphase behavior of supercritical CO2, even in the same reservoir. It touches on fundamentals of reservoir porosity and permeability, and even subsurface fluid flow but just barely. Just enough to be cool, stressed, over pressured and dense phased, more or less like the injected gas we care so much about.

D107 メッシュ・粒子のハイブリッド法による砕波の数値解析(OS10 混相流動)

This study is concerned with extension of numerical code called CRIMSON (Civa Refined Multiphase SimulatiON), which has been developed to evaluate multi-phase flow behaviors based on the recent CFD (computational fluid dynamics) techniques. The CRIMSON employs a finite-volume method combined with the high order interpolation scheme, CIVA (cubic-interpolation with area/volume coordinates). The CRIMSON solves gas-liquid two phases by a unified scheme of CUP (combined unified procedure). The conventional CIVA method has a problem of loosing interface sharpness in long-term calculation. In this study, the problem was solved by introducing the idea of the phase field method. For numerical analyzing splashing fluid, we also introduced the SPH particle method to the CRIMSON.

10502 CIVA法とSPH法のハイブリッド法による砕波のシミュレーション(産学における混相研究(1),OS.13 産学における混相研究)

This study is concerned with extension of numerical code called CRIMSON (Civa Refined Multiphase SimulatiON), which has been developed to evaluate multi-phase flow behaviors based on the recent CFD (computational fluid dynamics) techniques. The CRIMSON employs a finite-volume method combined with the high order interpolation scheme, CIVA (cubic-interpolation with area/volume coordinates). The CRIMSON solves gas-liquid two phases by a unified scheme of CUP (combined unified procedure). The conventional CIVA method has a problem of loosing interface sharpness in long-term calculation. In this study, the problem was solved by introducing the idea of the phase field method. For numerical analyzing splashing fluid, we also introduced the SPH particle method to the CRIMSON.

メタンハイドレート生産シミュレータの開発

Methane hydrate (MH) is being highlighted as next-generation hydrocarbon resources mainly because of its huge in place and cleanness. The Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium), which was organized to attain the exploration and exploitation of MH resources, has been implementing a variety of research projects. As part of such research projects, we have been developing a state-of-the-art numerical simulator (called ‘MH21-HYDRES’) for rigorously predicting MH dissociation and production performances. The main functions of this simulator and the efforts toward improving and verifying this simulator are introduced in this paper.The gas production from MH reservoirs is significantly different from that from conventional oil and gas reservoirs in terms of the mechanism and the phenomena, since (1) MH is a solid, (2) reservoir behaviors are associated with the chemical reactions such as MH dissociation/formation, and (3) reservoir properties, especially permeability, change drastically by MH dissociation. Therefore, it is impossible to predict MH reservoir performances by conventional oil and gas reservoir simulators, which lead to the development of the own numerical simulator specialized for MH reservoirs.Currently MH21-HYDRES can be applied to three-dimensional Cartesian and two-dimensional radial coordinate systems. This simulator can also deal with six components of methane, water, nitrogen, carbon dioxide, methanol and salt, and with five phases of gas, water, ice, MH and (precipitated) salt. The main features of this simulator are to calculate the kinetics of endothermic dissociation and exothermic formation reactions of MH as well as multi-phase flow behaviors resulting from these reactions. The simulator divides a target reservoir into multiple grid blocks, for which the pressure, temperature, water saturation, methanol and salt mass fractions, etc. are calculated solving the system of discretized non-linear equations for the component mass conservation and the overall energy conservation.To shorten the computational time, it is preferable to reduce the total number of grid blocks and hence to increase the size of grid blocks. On the other hand, larger grid blocks result in more significant numerical errors, which is more serious in a MH simulator than in a conventional oil and gas simulator. To resolve these problems inconsistent with each other, the Dynamic Local Grid Refinement (DLGR) function was incorporated into the simulator. DLGR enables a shorter computational time without reducing the accuracy of prediction, by allocating fine grid blocks only to the regions of importance where MH is being dissociated/formed at every time step. In addition, we are attempting to parallelize MH21-HYDRES utilizing the published MPI (message passing interface) and the parallelized solver for a linear equation system. Although the parallelized MH21-HYDRES is still in the prototype stage, using four processors, we could successfully achieve the computational speed that is about three times faster in comparison with serial processing.The international code comparison for MH simulators is being held, led by National Energy Technology Laboratory and U.S. Geological Survey. We are participating in this comparison to verify the performances of MH21-HYDRES. Although other simulators in this project show the deficiency for complex and large scale problems, MH21-HYDRES could provide reasonable solutions from the view point of the stability and robustness as well as the accuracy of calculated results, which may manifest the successful coding of this simulator.

Salt Effect on the High-Pressure Multiphase Behavior of the Ternary System (Ethene + Water + 2-Propanol)

At temperatures from (289 to 353) K, the ternary system (ethene + water + 2-propanol) is known to exhibit a region of liquid−liquid−vapor (L1L2V) equilibria at elevated pressures that is bordered by the lower ((L1 = L2)V) and upper (L1(L2 = V)) critical end point lines. This particular demixing effect is commonly known as “salting out by a supercritical gas”. In this work, the effect of adding different electrolytes on the pressure of both critical end points at (293 and 333) K is investigated.

Experimental study of granular flows in a rough annular shear cell

The study of granular flows in physics has always been important because of their recurring presence in nature and industry. However, the nonlinear and multiphase behavior exhibited by these particulate systems makes them hard to model and predict. Several experiments were conducted in the past to gain insight into granular flows. The current experimental work furthers this insight and specifically attempts to understand the effect of rough surfaces on granular flows, namely, their local flow behavior. Understanding this interaction can have implications on industrial-scale granular problems. In this work, a granular shear cell, a two-dimensional annular shear cell, was developed to conduct shear experiments where roughness is imposed on the driving surface and experimentally quantified. A digital particle tracking velocimetry data retrieval scheme was developed to extract solid fraction, velocity, and granular temperature data from the experiments as a function of the roughness factor and wheel rotation rate. In general, the steady-state results show the two distinct regions as expected-a high-velocity and dilute-gas-like kinetic region near the moving wall and a high-solid-fraction liquid-like frictional flow regime away from the moving wall. Parametric studies conducted show that the normalized slip near the moving wall decreases with increasing wall roughness and decreasing wall rotation rate. Slip is an important parameter which can be easily interpreted as momentum transfer or traction performance in granular systems related to wheel-terrain interaction, agricultural processing, and most notably granular lubrication.

Effect of Peng−Robinson Binary Interaction Parameters on the Predicted Multiphase Behavior of Selected Binary Systems

The ability of the Peng−Robinson equation of state (PR EOS) to calculate the high-pressure, multiphase behavior of select binary systems has been examined using K- and L-points (also referred to as critical end points) in phase space as key landmarks and adjusting the attractive term binary interaction parameter (δ12). The ethane + ethanol system showed a transition from type II behavior to type III behavior as δ12 increased, but the type V phase behavior exhibited experimentally could not be calculated with any value of δ12. The equation of state incorrectly calculated type V phase behavior for the methane + n-pentane system, which experimentally shows type I behavior. The type V behavior of the methane + n-hexane system was qualitatively calculated with δ12 = 0.014 giving the best fit to the experimental L-point while the type V behavior of the methane + n-heptane system was calculated, but the three-phase line failed to extend below the experimental four-phase point temperature and pressure (which expe...

Subsea Gas Lift in Deepwater Applications

This article, written by Technology Editor Dennis Denney, contains highlights of paper OTC 18820, "The Use of Subsea Gas Lift in Deepwater Applications," by Subash S. Jayawardena, George J. Zabaras, SPE, and Leonid A. Dykhno, Shell Global Solutions, prepared for the 2007 Offshore Technology Conference, Houston, 30 April-3 May. The paper has not been peer reviewed. Riser-base gas lift is used in subsea developments for production enhancement. It is an effective method to suppress severe slugging that occurs in flowlines with downhill inclination. In some cases, gas lift can aid blow-down for hydrate prevention. Gas lift is not always needed because its effectiveness depends on reservoir performance, fluid properties, seabed terrain, subsea architecture, and flowline and riser specifications. The need for gas lift, optimal operability, and system design should be assessed from various aspects, including flow assurance. A generic set of guidelines was developed on the basis of past experience with riser gas lift applications for different deepwater subsea projects and associated multiphase-flow phenomena. Introduction This paper discusses riser-base gas lift for deepwater subsea oil-production systems. The focus is how flow-assurance concerns affect various engineering decisions in designing a gas lift system. Riser-base gas lift is injection of a predetermined rate of gas from the host facility into the production flow-line (riser) at the seafloor. The reasons for gas lifting can vary, but the most important pertain to flow assurance, production enhancement, flow stabilization, and flowline depressurization. Why Gas Lift Is Needed The stages of a field's life should be studied to determine when to install and operate the gas lift system. Gas lift is not always beneficial; in some cases, increasing the gas rate may be detrimental to the performance of the subsea system. Production Enhancement. Gas lift for production enhancement lowers the flowline pressure. Typically, gas lift is needed with high water cuts in the flowlines, low-GOR fluids, and low-to-moderate production rates. The effectiveness is higher in systems with low production-system-inlet pressures. One major advantage of gas lift for production enhancement is that there are no moving parts in the subsea system, apart from valves and chokes. Compression for gas export is almost inevitable in any subsea development; therefore, the supply of lift gas during production is not a major issue. When to use gas lift for production enhancement should be determined by use of integrated (reservoir/wells/flowline) production modeling. The study also should include the water/gas injection to the reservoirs. Accuracy of flowline/riser pressure-drop and liquid-holdup calculations in multiphase-flow models and the accuracy of pressure/volume/temperature predictions are crucial. This accuracy becomes more important in larger-diameter flowlines with deepwater risers in which the multiphase behavior is different from that in smaller-diameter systems.

Catastrophic glacial multi-phase mass movements: a special type of glacial hazard

Abstract. Many glacier-related hazards are well typified and studied, but some events stand out from conventional classifications. The Kolka-Karmadon catastrophic event on 20 September 2002 in North Ossetia, North Caucasus, Russia is used as an example of a complex glacier failure exhibiting characteristics such as high mobility, long runout, ultrarapid movement and multiphase behaviour. We consider terminology protocol for glacier hazard classification and then, using the Kolka-Karmadon event and several other examples from around the world, we propose a new term for this family of events. Catastrophic glacier multi-phase mass movement (CGMM) is described and further illustrated by eight major events from Russia, Georgia, Peru, Chile, and Canada. CGMM have a combination of specific features: extraordinary velocities and long-distance runout despite low path angle; progressive fluidisation along travel path; superelevation and run-up of the moving mass, air blast wave in the avalanche flow phase; entrainment of available materials in its path, and the repeated nature of the event. CGMM events may affect areas remote from glaciers which were previously considered as safe.

Two-Dimensional Multiphase Behavior Induced by Sterically Hindered Conformational Optimization of Phenoxy-Substituted Phthalocyanines

Symmetrically substituted phthalocyanines (Pcs) with eight peripheral di-(tert-butyl)phenoxy (DTPO) groups self-organize on Ag(111) and Au(111) substrates into various assembly structures. These different structural phases were studied by scanning tunneling microscopy (STM). On the basis of high-resolution STM images, molecular models are provided for each phase that account for the observed unequal surface densities. Notably, the specificity of the studied Pc derivative featuring the peripheral phenoxy groups remarkably increases its conformational possibilities. Particularly, the rotational degrees of freedom allow all the DTPO substituents to be arranged above the plane of the Pc core, forming a bowl-like structure, which in turn enables the interaction of the Pc core with the metal substrate. The proximity of the Pc core to the metal substrate together with the steric entanglement between neighboring DTPO substituents causes significant retardation of the thermodynamic optimization of the conformations.

Micromechanical behaviors of duplex steel: in situ neutron diffraction measurements andsimulations

Recently, much attention has been paid to studying the micromechanical behavior ofmultiphase materials by virtue of their extensive engineering applications. A strongheterogeneity in stress exists in two-phase materials during loading due to the differentthermal expansion coefficients and the respective mechanical properties of each individualphase. For one duplex stainless steel under uniaxial compression, the distributions ofmicrostrains were characterized with the strain response of multiple reflections to theapplied external stress for each phase by employing in situ neutron diffractionexperiments. Based on these, the anisotropic elastoplastic properties of the duplex steelon microscales, i.e. phase size and grain size, were modeled using a two-phaseviscoplastic self-consistent (VPSC) model involving lattice rotation (texture evolution).Good agreement between predictions and neutron diffraction measurements wasfound. The stress partition between phases and orientated grains was discussed tocharacterize the phase stress and the grain-orientation-dependent stress, thus theparticular micromechanical properties of two-phase materials may be explored.

An evaluation of substrate degradation patterns in the composting process. Part 1: Profiles at constant temperature

This paper examines the patterns of 32 constant temperature substrate degradation profiles obtained from the composting literature, and evaluates the use of a single exponential model, a double exponential model and a non-logarithmic Gompertz model in describing their behaviour. Profiles were found to be predominantly either sigmoidal in shape, or to exhibit multi-phase behaviour, with a relatively small proportion of convex curves. Of the constant temperature profiles, 26 were either not well modelled by any of the above functions, or of such differing profiles that none of the above functions was applicable. Goodness of fit was measured using a normalised error function, and rated using a five-category descriptive scale, ranging from excellent to poor. No fits rated as excellent were observed. Fits rated as good were obtained for three data sets when using a single exponential function, for two data sets when using a double exponential function, and for one data set when using the non-logarithmic Gompertz function. The remainder of the fits were rated as moderate to poor. It is concluded that the evidence supporting the use of the single exponential model, the double exponential model or the non-logarithmic Gompertz model to describe substrate degradation profiles generated at constant temperature is limited. Further work is suggested in order to establish standard procedures and a standard simulated composting mixture for substrate degradation studies and to build a more comprehensive set of long-term substrate degradation profile data at constant temperature, and under non-limiting moisture and oxygen concentration conditions.

Transient multiphase processes during the explosive eruption of basalt through a geothermal borehole (Námafjall, Iceland, 1977) and implications for natural volcanic flows

Experimental and numerical studies have shown that vertical flows of gas–particle mixtures are characterized by transient behavior, with development of waves of high particle concentration separated by regions of relatively clean gas. In contrast, most models of explosive flow in volcanic conduits either treat the multiphase mixture as a single fluid (pseudo-fluid approximation) and/or assume steady flow, thereby eliminating the potential for time-dependent effects related to multiphase dynamics. The 8 September 1977 explosive eruption of basaltic tephra through a geothermal borehole (Námafjall, Iceland) provides a unique test case for multiphase volcanic processes, given that its vertical extent (∼ 1 km) is similar to that of natural volcanic conduits and its geometry is exactly known. We model this eruption by solving separate, time-dependent governing equations for conservation of mass, momentum, and energy of the gas and particle phases, allowing for drag and heat transfer between the phases. Model results are consistent with the development of transient waves of high particle concentration that propagate up the borehole, resulting in complex compressible flow phenomena along with ejection of particles in pulses in a manner that is consistent with observations at Námafjall. These transient processes occur even though the influx of gas and particles at the base of the borehole is treated as constant. Our results indicate that transient multiphase behavior is likely to be common in volcanic conduit flows, and that a key topic of future research is quantifying the types of time-dependent behaviors and their impacts on eruption column dynamics.

Chemical pressure effect on CMR behavior of Sr substituted [formula omitted

A series of systematic substitution of isovalent Sr ion into the Ca site of La 0.67 Ca 0.33 - x Sr x MnO 3 system has been studied for different x values ranging from x = 0.00 , 0.033 , 0.066 , … , 0.33 . It is observed that at x = 0.066 , the system begins to exhibit multiphasic behavior with the onset of X-ray shoulder peak at 2 θ value of 32 . 96 ∘ . In this paper, we report low field SQUID magnetization behavior and electrotransport properties of the above system with x = 0.00 , 0.033 and 0.066. It is noted that larger cationic size ( Sr 2 + ) does not allow the system to attain low bandwidth, which is the important parameter to control the electric and magnetic properties including Curie temperature ( T c ) and metal insulator transition temperature ( T IM ) . The role of Sr 2 + ion substitution as larger radius with respect to Ca 2 + ion in the La 0.67 Ca 0.33 - x Sr x MnO 3 system can specifically be assigned to enhance the electron bandwidth ( W ), which promotes higher T c and T IM . In addition to this, an interesting spin glass cluster and transition phenomena are observed at low temperature region ( ≈ 50 K ) for x = 0.066 .