Influence of a surfactant or salt on phase inversion in a water–oil pipe flow

Phase inversion experiments have been performed with a water–oil flow through a pipe to study the effect of the addition of a surfactant or of salt on the critical dispersed phase volume fraction (at the point of phase inversion). The addition of a surfactant caused a small change in the critical volume fraction, but the general form of the ambivalence region in the inversion map remained the same. The influence of salt was negligible.     

Wall friction and effective viscosity of a homogeneous dispersed liquid–liquid flow in a horizontal pipe

Homogenous oil in water dispersion has been investigated in a horizontal pipe. The mean droplet size is 25 μm. Experiments were carried out in a 7.5‐m‐long transparent pipe of 50‐mm internal diameter. The wall friction has been measured and modeled for a wide range of flow parameters, mixture velocities ranging from 0.28 to 1.2 m/s, and dispersed phase volume fractions up to 0.6, including turbulent, intermediate, and laminar regimes. Flow regimes have been identified from velocity profiles measured by particle image velocimetry in a matched refractive index medium. It is shown that the concept of effective viscosity is relevant to scale the friction at the wall of the dispersed flow. Based on mixture properties, the friction factor follows the Hagen‐Poiseuille and the Blasius' law in laminar and turbulent regimes, respectively. Interestingly, the transition toward turbulence is delayed as the dispersed phase fraction is increased. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Inception and termination of the core‐annular flow pattern for oil‐water downflow through a vertical pipe

Different flow patterns for lube oil–water and for kerosene‐water downflow through a vertical glass tube have been analyzed with the help of flow visualization. Core‐annular flow is the dominant flow regime, with oil forming the core, and water is forming the wall film. When the velocities are increased, transition to slug flow and transition to dispersed flow are found. The waves found during the transition to slug flow depend on oil viscosity: axisymmetric bamboo waves are seen in kerosene‐water downflow and the waves are asymmetric in case of lube oil–water flow where they have a cork‐screw shape. Based on the experimental observations, simple mathematical models have been proposed for predicting the flow pattern transition curves. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Gas holdup for high gas velocities in a gas–liquid cocurrent upward‐flow system

Gas holdup has been measured in an 83‐mm diameter, 2.2‐m high column at high gas superficial velocities — 0.22 to 2.7 m/s — and at liquid (water) superficial velocities of 0 to 0.47 m/s, by means of a differential pressure transducer. The equation of Hills (1976) based on the slip velocity gives good predictions of the gas holdup for 0.1 ≤ E_g ≤ 0.4. However, the holdups predicted by this approach are considerably higher than the experimental values at gas velocities high enough that E_g > 0.4. Other equations from the literature are also shown to be inadequate. The new data and earlier data at high gas velocities are therefore correlated with a new dimensional equation for U_l ≤ 0.23 m/s.     

Phase distribution in dispersed liquid–liquid flow in vertical pipe: Mean and turbulent contributions of interfacial force

We applied an Eulerian–Eulerian two‐fluid model on an upward dispersed oil–water flow in vertical pipe with 80 mm diameter and 2.5 m length. The numerical profiles of the radial distribution of the oil drops at 1.5 m from the inflow are compared to the experimental data of Lucas and Panagiotopoulos (Flow Meas Instrum. 2009;20:127–135) This article analyzes the roles of turbulence and interfacial forces on the phase distribution phenomenon. In liquid–liquid flow the relative velocity is low and the distribution of the dispersed phase is mainly governed by the turbulence. This work highlights the important role of the turbulent contribution obtained by averaging the added mass force on the radial distribution profiles of the oil drops. The numerical results present improved profiles of the dispersed phase comparing to the experimental data when this turbulent contribution is taken into account in the momentum balance. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4214–4223, 2017     

Bubble Size Distributions for Dispersed Air – Water Flows in a 100 mm Horizontal Pipeline

The bubble size distributions of air dispersed in water flowing in a 100 mm horizontal pipeline were studied. Size distributions were obtained with a high‐speed digital camera at axial positions 0.5, 15.3 and 42.3 m from the air injection point. Air was injected into the pipeline through a narrow tube extending into the pipe, perpendicular to the pipe axis. The effects of average water velocity, air concentration, and injection nozzle diameter on the evolution of bubble size distribution with axial pipe position were studied. For the lowest air concentration of 0.07%, equilibrium bubble size distributions were dependent only on water velocity. Nozzle injection diameter did not affect the downstream bubble size distributions at air concentrations of 0.07% and 0.3%. Levich's break‐up theory was found to over‐predict the experimental d_max for each test condition.     

Sensor‐based flow pattern detection—gas–liquid–liquid upflow through a vertical pipe

Flow distribution during gas–liquid–liquid upflow through a vertical pipe is investigated. The optical probe technique has been adopted for an objective identification of flow patterns. The probability density function (PDF) analysis of the probe signals has been used to identify the range of existence of the different patterns. Dispersed and slug flow have been identified from the nature of the PDF, which is bimodal for slug flow and unimodal for dispersed flow. The water continuous, oil continuous, and emulsion type flow distributions are distinguished on the basis of the PDF moments. The method is particularly useful at high flow rates where visualization techniques fail. Based on this, a flow pattern detection algorithm has been presented. Two different representations of flow pattern maps have been suggested for gas–liquid–liquid three phase flow. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3362–3375, 2014     

Drag reduction phenomenon in viscous oil‐water dispersed pipe flow: Experimental investigation and phenomenological modeling

An experimental study on drag‐reduction phenomenon in dispersed oil‐water flow has been performed in a 26‐mm‐i.d. Twelve meter long horizontal glass pipe. The flow was characterized using a novel wire‐mesh sensor based on capacitance measurements and high‐speed video recording. New two‐phase pressure gradient, volume fraction, and phase distribution data have been used in the analysis. Drag reduction and slip ratio were detected at oil volume fractions between 10 and 45% and high mixture Reynolds numbers, and with water as the dominant phase. Phase‐fraction distribution diagrams and cross‐sectional imaging of the flow suggested the presence of a higher amount of water near to the pipe wall. Based on that, a phenomenology for explaining drag reduction in dispersed flow in a flow situation where slip ratio is significant is proposed. A simple phenomenological model is developed and the agreement between model predictions and data, including data from the literature, is encouraging. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Investigation of the specific interfacial area of a palm oil–water system

Oil–water dispersions have many important applications in the chemical and oleochemical industries. A measure of the specific interfacial area of the dispersed phase provides a direct indication of the quality of the dispersion. In this study, the specific interfacial area for the palm oil–water system was determined using a microscopic technique. The effects of oil volume fraction, agitation speed and temperature on the specific interfacial area have been determined experimentally and an empirical correlation to predict the total specific interfacial area under different operating conditions is proposed. This correlation can be used in the design of reaction and non‐reaction systems using palm oil–water dispersions. Copyright © 2004 Society of Chemical Industry     

水平管道气液两相段塞流参数计算的精确模型

分析了水平管内气液两相段塞流的运动特性和形态特征以及段塞单元内部的速度分布规律,建立了水平管路气液两相段塞单元的物理模型。将一个完整的段塞流单元分为液相段塞区和液层/气泡区,建立了液相段塞区的质量和动量守恒方程,计算了其压降和持液率;对液层区,模型考虑液层厚度分布不均(坡状液层)对参数计算的影响,通过建立局部控制方程,推导了液层高度随流动方向坐标变化的表达式,并将持液率和湿周写成液层高度的函数。通过与实验和其他模型的计算结果对比,本文建立的模型可以对压降和持液率有更准确的预测结果。     

油气水三相段塞流与滚动波流型的转变

Compared with gas-liquid two-phase flow,oil-gas-water three-phase flow is much more complex. There is immiscible oil-water,whose interaction and dispersion greatly affects the flow characteristics. The slug flow pattern of oil-gas-water three-phase and its flow pattern transition were studied in a 95 m long,51 mm i. d. horizontal pipe. The oil-gas-water three-phase slug flow pattern could be classified into five sub-flow patterns. The slug flow was W/O or O/W one during its transition to roll wave,which was three-layer flow pattern without mixed-phase on the interface. An even larger superficial gas velocity was needed for the transition boundary of slug flow and roll wave flow when the superficial liquid velocity is large. Besides,the region of roll wave flow pattern became smaller. The above-mentioned transition only happened when the water cut of liquid was between 30% and 70%. At the same superficial liquid velocity,there appeared a minimum superficial gas velocity corresponding to the transition of flow pattern when the water cut of liquid was between 40% and 50%.     

Bubble shape,gas flow and gas–liquid mass transfer in pulp fibre suspensions

Gas–liquid mass transfer in pulp fibre suspensions in a batch‐operated bubble column is explained by observations of bubble size and shape made in a 2D column. Two pulp fibre suspensions (hardwood and softwood kraft) were studied over a range of suspension mass concentrations and gas flow rates. For a given gas flow rate, bubble size was found to increase as suspension concentration increased, moving from smaller spherical/elliptical bubbles to larger spherical‐capped/dimpled‐elliptical bubbles. At relatively low mass concentrations (C_m = 2–3% for the softwood and C_m ? 7% for the hardwood pulp) distinct bubbles were no longer observed in the suspension. Instead, a network of channels formed through which gas flowed. In the bubble column, the volumetric gas–liquid mass transfer rate, k_La, decreased with increasing suspension concentration. From the 2D studies, this occurred as bubble size and rise velocity increased, which would decrease overall bubble surface area and gas holdup in the column. A minimum in k_La occurred between C_m = 2% and 4% which depended on pulp type and was reached near the mass concentration where the flow channels first formed.     

Ceria in catalysis: From automotive applications to the water–gas shift reaction

Ceria is a crucial component of automotive catalysts, where its ability to be reduced and re‐oxidized provides oxygen storage capacity. Because of these redox properties, ceria can greatly enhance catalytic activities for a number of important reactions when it is used as a support for transition metals. For reactions that use steam as an oxidant (e.g., the water–gas‐shift reaction and steam reforming of hydrocarbons), rates for ceria‐supported metals can be several orders of magnitude higher than that for ceria or the transition metal alone. Because the redox properties of ceria are strongly dependent on treatment history and the presence of additives, there are significant opportunities for modifying catalysts based on ceria to further improve their performance. This article will review some of the contributions from my laboratory on understanding and using ceria in these applications. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Evaluating the performance of a portable water–mist fire extinguishing system with additives

This study investigates how high‐pressure water–mist system discharge methodologies influence the fire extinction performance for pan pool fires and the corresponding mechanisms of restraining fire. The fire source is a pool‐fire burner. Fine water spray is injected using a portable device. The additive in the water–mist is neither toxic nor corrosive. All the tests are regarded as fuel controlled. The fire test parameters are fuel type, nozzle discharge angle, and additive solution volume. The fuels used are heptane, gasoline, and diesel. Nozzle discharge angles are 30, 45, and 60° with respect to the ground. Additive solution volumes are 0% (pure water), 3, 6, and 10%. Test results indicate that the nozzle discharge angle and additive solution volume in a water–mist fire extinction system play a significant role. Fire extinguishing efficiency is influenced by mist effects and the additive. Furthermore, the water–mist system can reduce radiation and can provide good protection for operators using portable fire extinguishing equipment. Copyright © 2008 John Wiley & Sons, Ltd.     

Influence of an orifice on liquid–liquid two phase flow

The present study aims an in depth investigation of liquid–liquid horizontal flow through an orifice. Initial studies have been directed to observe the influence of the orifice plate on the phase distribution of the two liquids in the pipe. The flow patterns have been identified using an optical probe along with photographic technique. The probability density function (PDF) analysis of the random signals obtained from the optical probe has been adopted to quantify the observations. The cross‐correlation function between the probe signals upstream and downstream of the orifice has been estimated to check the repeatability of the phenomenon. The inception of dispersion in the downstream section has been observed to occur in the stratified region of the upstream. The use of an orifice as a homogenizer as well as a feasible flow‐metering device for liquid–liquid flow has been encouraged by experimental results.     

High temperature water–gas shift reaction over hollow Ni–Fe–Al oxide nano-composite catalysts prepared by the solution-spray plasma technique

The effect of Fe content in Ni–Fe–Al oxide nano-composites prepared by the solution-spray plasma technique on their catalytic activity for the high temperature water–gas shift reaction was investigated. The composites showed a hollow sphere structure, with highly dispersed Fe–Ni particles supported on the outer surface of the spheres. When the water–gas shift reaction was performed over an Ni–Al oxide composite catalyst without Fe, undesired CO methanation took place predominantly compared to the water–gas shift reaction, and significant amounts of hydrogen were consumed. When appropriate amounts of Fe were added to the Ni–Al oxide composite catalyst during the plasma process, methanation was suppressed remarkably, without serious loss of activity for the water–gas shift reaction. The catalyst was characterized by STEM, XRD and H₂ chemisorption measurements.     

Dispersed phase holdup and bubble size distributions in gas–liquid cocurrent upflow and countercurrent flow in reciprocating plate column

Dispersed phase holdup and the bubble size distribution were measured in a reciprocating plate column under cocurrent upflow and countercurrent flow of gas and liquid phases. The response of the system to a variation in design and operating conditions was found similar to that for liquid–liquid contacting; the magnitude of response, however, differed significantly between them. Taking into consideration the dominant forces encountered in gas–liquid dispersions, the experimental data are satis–factorily correlated in terms of Froude, Weber and Gallileo numbers.