Suppressing intermittent flow patterns and reducing pressure loss in two-phase horizontal pipe flow using surfactants

The addition of small concentrations of surfactant to an air/water two-phase flow through a 2 inch Schedule 40 (0.052 m-id) smooth PVC pipe resulted in significant changes to the flow pattern map and pressure loss of the system. Sodium dodecylsulfate was added to an air/water two-phase flow at several concentrations at or below the critical micelle concentration. As the surfactant concentration increased, the amount of foam generated in the flow increased, and several flow patterns not previously reported were observed. There was a reduction in the conditions under which intermittent flow patterns developed. It is proposed that the ability of the foam to dissipate local pressure gradients caused the reduction in the occurrence of intermittent flow. Pressure loss was measured for two-phase air/water stratified flow with and without surfactant. Addition of surfactant reduced the pressure loss in two-phase flow at concentrations that have no effect on single-phase, water only pressure loss. It is proposed that the liquid surface is less easily deformed in surfactant-containing flows due to surface concentration gradients created by interfacial forces, resulting in lower interfacial friction

Particles, Drops, and Bubbles Moving Across Sharp Interfaces and Stratified Layers

International audienceRigid or deformable bodies moving through continuously stratified layers or across sharp interfaces are involved in a wide variety of geophysical and engineering applications, with both miscible and immiscible fluids. In most cases, the body moves while pulling a column of fluid, in which density and possibly viscosity differ from those of the neighboring fluid. The presence of this column usually increases the fluid resistance to the relative body motion, frequently slowing down its settling or rise in a dramatic manner. This column also exhibits specific dynamics that depend on the nature of the fluids and on the various physical parameters of the system, especially the strength of the density/viscosity stratification and the relative magnitude of inertia and viscous effects. In the miscible case, as stratification increases, the wake becomes dominated by the presence of a downstream jet, which may undergo a specific instability. In immiscible fluids, the viscosity contrast combined with capillary effects may lead to strikingly different evolutions of the column , including pinch-off followed by the formation of a drop that remains attached to the body, or a massive fragmentation phenomenon. This review discusses the flow organization and its consequences on the body motion under a wide range of conditions, as well as potentialities and limitations of available models aimed at predicting the body and column dynamics

Comparison between Two Surfactants (Sodium Oleate and Sodium Stearate)As Drag Reducing Agent in Water System

This project aim is to study the effectiveness of surfactants which are Sodium Oleate and Sodium Stearate as Drag reducing agents in water injection system. In the life reservoir, there will come to a point where it will be no longer being able to produce for hydrocarbon. At this stage, we usually prefer to use secondary recovery to boost up the performance of the reservoir back. One of the many choices for secondary recovery is by using water injection. In water injection system, it will require a very long pipeline to inject water into reservoir. What the engineers are being concern about is the large pressure drop that might happen along the pipeline. Theoretically explain, the large pressure loss is caused by the frictional forces between the walls of the pipe with the turbulence fluid flowing through it. it is found that the longer the pipeline, the higher the pressure drop will be. So by making two different types of surfactants as DRA, which are Sodium Oleate and Sodium Stearate, we will be able to investigate which one performed better as DRA in water injection system. The experiment is done in a lab consist of 4metre pipeline with two pressure gauges which will measure the pressure drop of liquid. Before that, a total of 8 concentrations of Sodium Oleate and Sodium Stearate are prepared using distilled water and magnetic stirrer. For every concentration, we made two samples so that we can take average measurement of respective concentrations. From the experiment done, it is shown that Sodium Stearate shows a better result performing as DRA compared to Sodium Oleate because at 600ppm, Sodium Stearate gives the lowest average pressure drop which is 7.25psi. While for average flow rate, Sodium Stearate gives the highest at 400ppm which is 37.41gpm. The highest %DR and %FI for Sodium Stearate are 47.22% and 42.66% respectively. So in conclusion, Sodium Stearate shows a better ability as DRA in water pipeline system compared to Sodium Oleate. This shows the study of surfactants DRA is important because it can help to reduce drag problem which is a major problem in our oil industry

INVESTIGATION OF MICRO BUBBLE FOR THE REMOVAL OF SUSPENDED PARTICLE AND ENHANCEMENT OF DISSOLVED OXYGEN IN POLLUTED WATER

Filtration and precipitation are generally used in wastewater treatment to separate pollutants. However, they are not cost effective and have problems of filter waste and time consumption. The smaller particles are left even after a filtration process, depending upon the porosity of the filter. This research proposes a new approach of using compressed air to lift up micro suspended particles in polluted water. The novelty of the approach is in its sustainability, cost effectiveness and faster solution to micro pollutant separation. Air is forced through a submerged micro diffuser to produce micro bubbles, which flow upward and entrain suspended particles to separate them from water. The study was carried experimentally and a lab test rig was designed and implemented. Bubble size plays an important role in moving suspended particles upwards due to the buoyancy force, which in turn depends upon the vertical component of bubble velocity. Generally, the larger bubbles tend to change shape due to high buoyancy force. The bubble velocity is characterized by the Froude number and Reynolds number. The strategies to control the bubble size in monodispersed (single size) and polydispersed (multi size) cases are presented in this research. To simulate the real wastewater physiochemical characteristics (surface tension, density, viscosity, etc), Glycerin is added to distilled water in various volume fractions of 0.1% to 0.5%. The relationship between air pressure, vertical and horizontal velocities, as well as bubble size is studied. These parameters (bubble diameter, vertical velocity) lead to high effectiveness of suspended particles separation, and are validated by measuring the low concentration of pollutant (PPM), corresponding to the turbidity level. The amount of suspended particles in relation to turbidity has been studied and it is found that the turbidity level of 6.9 NTU decreases to 3.66 NTU, using 1-10 micron porous sintered glass as a submerged diffuser and at 12 10-3 m3/min air flow. In most biological wastewater treatment systems, a submerged diffuser is used to provide oxygen and mixing to degrade the organic matter. In this study, the effectiveness of micro diffusers in the degradation of organic matter was investigated. The nitrification performance using both micro and macro diffusers was evaluated by measuring ammonium-nitrogen (NH4-N) and nitrate-nitrogen (NO3-N). The experimental values were compared with the theoretical values derived from the kinetic calculations. Two batch experiments were conducted for the estimation of the kinetic parameters for the degradation and the nitrification of organic matter at 1 hour, 3 hours, 6 hours, and 24 hours until 48 hours, in steps of 3 hours for each batch of experiments. From the measurement results, the degradation kinetic COD parameter (kCOD) of the micro diffuser was found to be 1.46 times higher than the macro diffuser. Therefore the degradation kinetics of soluble COD parameter (ksCOD) of the micro diffuser was found to be 1.5 times higher than macro diffuser. The difference between micro and millimeter diffusers in removed COD was approximately 6%. , and in removed sCOD was approximately 16%. The main data parameters in Nitrification of wastewater were ammonium and nitrate. The measurement results of ammonium and nitrate using micro diffuser was achieved at 3% higher than macro diffuser

Determination of Interfacial Tension of Immiscible Two-Phase, Oil-Water System Subjected to Polymeric Drag additives

In this paper, the determination of interfacial tension of immiscible two-phase oil-water system subjected to polymeric drag additives was investigated. Polymeric drag reducing additives (PDRA) have been discovered in the late 1940s, where its first large-scale commercial utilization was implemented in the Trans-Alaskan Pipeline System (TAPS) three decades after its discovery by Toms. The ability of polymer solution to modify the viscosity of the flowing medium translates into its assistance of altering the flow properties during the transportation of fluids. During the process, PDRA promoted the bubbly and dispersed flow into stratified regime, where oil-water is separated via a pronounced interfacial boundary. In this condition, the nature of the interfacial tension is unknown due to the changes caused by the dilution of PDRA into the flowing medium. This research presents the study on the rheological properties of the partially hydrolysed polyacrylamide (PHPA) solution that acted as PDRA. The experimental work consists of viscometry and the pendant drop analysis. Three different concentration; 10 ppm, 50 ppm and 70 ppm from a 1000 ppm master solution of PHPA were tested at elevated temperature to study its rheological properties as well as the interfacial tension of the oil-water phase. From the results, it is clear that higher concentration of PHPA leads to higher viscosity. All solutions that were investigated in this study exhibited “shear thinning”, and is proven as the n value calculated is less than 1. From the results, the PHPA solutions investigated behaved in a non-Newtonian manner that abide the Power Law. The addition of all the PHPA solution had decreased the interfacial tension of the oil-water syste

Cavity and Wake Flows

The phenomenon of wake formation behind a body moving through a fluid, and the associated resistance of fluids, must have been one of the oldest experiences of man. From an analytical point of view, it is also one of the most difficult problems in fluid mechanics. Rayleigh, in his 1876 paper, observed that "there is no part of hydrodynamics more perplexing to the student than that which treats of the resistance of fluids." This insight of Rayleigh is so penetrating that the march of time has virtually left no mark on its validity even today, and likely still for some time to come. The first major step concerning the resistance of fluids was made over a century ago when Kirchhoff (1869) introduced an idealized inviscid-flow model with free streamlines (or surfaces of discontinuity) and employed (for steady, plane flows) the ingenious conformal-mapping technique that had been invented a short time earlier by Helmholtz (1868) for treating two-dimensional jets formed by free streamlines. This pioneering work offered an alternative to the classical paradox of D’Alembert (or the absence of resistance) and laid the foundation of the free-streamline theory. We appreciate the profound insight of these celebrated works even more when we consider that their basic idea about wakes and jets, based on a construction with surfaces of discontinuity, was formed decades before laminar and turbulent flows were distinguished by Reynolds (1883), and long before the fundamental concepts of boundary-layer theory and flow separation were established by Prandtl (1904a). However, there have been some questions raised in the past, and still today, about the validity of the Kirchhoff flow for the approximate calculation of resistance. Historically there is little doubt that in constructing the flow model Kirchhoff was thinking of the wake in a single-phase fluid, and not at all of the vapor-gas cavity in a liquid; hence the arguments, both for and against the Kirchhoff flow, should be viewed in this light. On this basis, an important observation was made by Sir William Thomson, later Lord Kelvin (see Rayleigh 1876) "that motions involving a surface of separation are unstable" (we infer that instability here includes the viscous effect). Regarding this comment Rayleigh asked "whether the calculations of resistance are materially affected by this circumstance as the pressures experienced must be nearly independent of what happens at some distance in the rear of the obstacle, where the instability would first begin to manifest itself." This discussion undoubtedly widened the original scope, brought the wake analysis closer to reality, and hence should influence the course of further developments. An expanded discussion essentially along these lines was given by Levi-Civita (1907) and was included in the survey by Goldstein (1969). Another point of fundamental importance is whether the Kirchhoff flow is the only correct Euler (or outer) limit of the Navier-Stokes solution to steady flow at high Reynolds numbers. If so, then a second difficulty arises, a consequence of the following argument: We know that the width of the Kirchhoff wake grows parabolically with the downstream distance x, at a rate independent of the (kinematic) viscosity u. If Prandtl’s boundary-layer theory is then applied to smooth out the discontinuity (i.e. the vortex sheet) between the wake and the potential flow, one obtains a laminar shear layer whose thickness grows like (ux/U)^-1/2 in a free stream of velocity U. Hence, for sufficiently small u/U the shear layers do not meet, so that the wake bubble remains infinitely long at a finite Reynolds number, a result not supported by experience. (For more details see Lagerstrom 1964, before p. 106, 131; Kaplun 1967, Part II.) The weaknesses in the above argument appear to lie in the two primary suppositions that, first, the free shear layer enveloping the wake would remain stable indefinitely, and second (perhaps a less serious one), the boundary-layer approximation would be valid along the infinitely long wake boundary. Reattachment of two turbulent shear layers, for instance, is possible since their thickness grows linearly with x. By and large, various criticisms, of the Kirchhoff flow model have led to constructive refinements of the free-streamline theory rather than to a weakening of the foundation of the theory as a valuable idealization. The major development in this direction has been based on the observation that the wake bubble is finite in size at high Reynolds numbers. (The wake bubble, or the near-wake, means, in the ordinary physical sense, the region of closed streamlines behind the body as characterized by a constant or nearly constant pressure.) To facilitate the mathematical analysis of flows with a finite wake bubble, a number of potential-flow models have been introduced to give the near-wake a definite configuration as an approximation to the inviscid outer flow. These theoretical models will be discussed explicitly later. It suffices to note here that all these models, even though artificial to various degrees, are aimed at admitting the near-wake pressure coefficient as a single free parameter of the flow, thus providing a satisfactory solution to the state of motion in the near part of the wake attached to the body. On the whole, their utility is established by their capability of bringing the results of potential theory of inviscid flows into better agreement with experimental measurements in fluids of small viscosity. The cavity flow also has a long, active history. Already in 1754, Euler, in connection with his study of turbines, realized that vapor cavitation may likely occur in a water stream at high speeds. In investigating the cause of the racing of a ship propeller, Reynolds (1873) observed the phenomenon of cavitation at the propeller blades. After the turn of this century, numerous investigations of cavitation and cavity flows were stimulated by studies of ship propellers, turbomachinery, hydrofoils, and other engineering developments. Important concepts in this subject began to appear about fifty years ago. In an extensive study of the cavitation of water turbines, Thoma (1926) introduced the cavitation number (the underpressure coefficient of the vapor phase) as the principal similarity parameter, which has ever since played a central role in small-bubble cavitation as well as in well-developed cavity flows. Applications of free-streamline theory to finite-cavity flows have attracted much mathematical interest and also provided valuable information for engineering purposes. Although the wake interpretation of the flow models used to be standard, experimental verifications generally indicate that the theoretical predictions by these finite-wake models are satisfactory to the same degree for both wake and cavity flows. This fact, however, has not been widely recognized and some confusion still exists. As a possible explanation, it is quite plausible that even for the wake in a single-phase flow, the kinetic energy of the viscous flow within the wake bubble is small, thus keeping the pressure almost unchanged throughout. Although this review gives more emphasis to cavity flows, several basic aspects of cavity and wake flows can be effectively discussed together since they are found to have many important features in common, or in close analogy. This is in spite of relatively minor differences that arise from new physical effects, such as gravity, surface tension, thermodynamics of phase transition, density ratio and viscosity ratio of the two phases, etc., that are intrinsic only to cavity flows. Based on this approach, attempts will be made to give a brief survey of the physical background, a general discussion of the free-streamline theory, some comments on the problems and issues of current interest, and to point out some basic problems yet to be resolved. In view of the vast scope of this subject and the voluminous literature, efforts will not be aimed at completeness, but rather on selective interests. Extensive review of the literature up to the 1960s may be found in recent expositions by Birkhoff & Zarantonello (1957), Gilbarg (1960), Gurevich (1961), Wehausen (1965), Sedov (1966), Wu (1968), Robertson & Wislicenus (1969), and (1961)

Development of an inverted stabilised bubble fluidised bed reactor for adsorptive processes

Granular Activated Carbon (GAC) is used in packed beds to treat trace quantities of icropollutants. Many years of research and industrial use has ensured that it is highly effective as a water treatment process. However, GAC is expensive and economic considerations mean it has to be recovered and re-used Powdered Activated Carbon (PAC; is a cheaper alternative but the particle size range means it is unsuitable for packed bed applications. This thesis describes a novel method for utilising PAC to treat micropollutants. By contacting carbon paracles with air bubbles, under conditions o.lrotational shear and a binding agent, oleyl alcohol, carbon-coated air bubbles form which remain stable while agitated byflowing water. A stabilised air bubble can be visualised as a phere with an impervious core (the air bubble), surrounded by a thin layer of porous matehal (PAC). Theory dictates that all these stabilised air bubbles can be moved counter-currently to a contaminated stream, higher throughputs than conventional packed beds are possible. Several aspects of this process are investigated. Bubble generation is critical and so the literature was reviewed to explain the mechanisms involved Practical use was made of this knowledge in designing a larger bubble generator. Transferring the coated-bubbles to a contacting column was difficult. Problems associated with the various methods employed are described and recommendations are made for improvement. The contacting column was used to assess the stability and adsorptive capacity of the bubbles. The possibility of counter-current flow using stabilised air bubbles was also evaluated and found to be incompatible with the current column design. The stabilised bubbles collected in the column resembled an inverted fluidised bed. Experiments were performed to test Richardson and Zaki's hydrodynamic laws for conventional fluidised beds were applicable to inverted beds. The adsorptive capacity of the bubbles was assessed by dosing the water with trace levels of phenol and p-chlorophenol. Samples taken from before and after the fluidised bed were analysed and compared. The results were inconclusive, although the concentration profile produced indicated that flow through the bubble bed was piston-flow

Development of an optimised integrated underbalanced drilling strategy for cuttings transport in gas-liquid flow through wellbore annuli.

Although understanding the relationship between gas-liquid two-phase fluid flows and the effects of the major drilling variables is critical to optimising underbalanced drilling (UBD) operations, to date, this has been an area of limited research and knowledge. This study contributes to the limited knowledge base by: 1) determining the key operational drilling parameters which shape the gas-liquid two-phase multiphase flow behaviour characteristics during UBD operations, 2) evaluating the most critical operational issues that have impacted the implementation of global UBD programmes, and 3) investigating the Newtonian and non-Newtonian gas-liquid two-phase flow patterns which affect the wellbore hydraulics and cuttings transport efficiency during UBD operations. Thus, this study developed a rigorous integrated strategy for maximising the efficiency of UBD for the transport of cuttings in gas-liquid two-phase flow through wellbore annuli. An experimental approach was applied to analyse and evaluate the relationship between the gas-liquid two-phase flow patterns and the major operational drilling parameters (gas and liquid flowrates, fluid rheology, inner pipe rotation, pipe inclination angle, pipe eccentricity and solid particle size and density) and to investigate their influence and interaction on the fluid flow dynamics and solids transport mechanisms in horizontal and inclined annuli. Experimental results revealed that drilling fluid flowrate along with fluid flow pattern are the most prominent parameters that strongly influence the cuttings transport efficiency within wellbore annuli. Annuli cleaning requirements for a concentric annulus was found to be lower than that required for an eccentric annulus for both Newtonian and non-Newtonian fluids. Pipe inclination angle was shown to affect hole cleaning, with the degree of its effect being significantly influenced by the drilling fluid properties, prevailing gas-liquid fluid flow pattern and cuttings transport mechanism. Moreover, inner pipe rotation was observed to improve cuttings transport in both horizontal and inclined eccentric annuli to varying extents. Experimental evidence was supplemented with a theoretical approach. Flow pattern dependent multi-layered mathematical models applicable for any level of pipe eccentricity were used for the different cuttings transport mechanisms existing in the different fluid flow patterns (dispersed bubble, bubble, and slug), offering a unique method to evaluate cuttings transport efficiency and wellbore hydraulics performance for UBD operations. A favourable comparison was observed between the experimental data and proposed flow pattern dependent multi-layered mathematical models with an error margin of ±15%. This research has generated new knowledge and created value through mapping the factors influencing particle transport and by evaluating the fluid-particle dynamics (fluid forces, gas-liquid fluid flow patterns and particle transport mechanisms) for flow in wellbore annuli. It has further identified and evaluated the effect of gas-liquid two-phase fluid flow patterns on fluid-particle transport dynamics which results in areas of preferential flows and stagnation zones. It also proposed a systematic solution to the governing equations for the simultaneous flow of gas-liquid two-phase fluids and solid particles in wellbore annuli. Overall, the mapping of the major operational drilling parameters and their influence and interdependencies on wellbore dynamics and cuttings transport efficiency in the context of gas-liquid fluid systems, provides a tool for the prediction of cuttings transport mechanism, determination of the stationary bed height, and calculation of the annuli pressure losses. Therefore, wellbore pressure evaluation and management and hole cleaning requirements for UBD operations can be addressed

Investigating the Effect of Different Salinity Levels of Water in Waterflooding on Drag Reducing Agent Extracted from Natural Waste Materials

The use of drag reducing agent (DRA) as an additive in oil and gas industry has become famous and widely used nowadays. The usage of DRA is not limited in pipeline only, it has been also used in waterflooding or water injection system. However, information on the usage and reliability of natural polymers as DRA in water injection system are still limited. In this paper, polymer was extracted from natural waste materials (coconut residue) for the purpose of producing the DRA. Other than that, the effectiveness of the DRA was tested in different properties of water since the parameters of water used in waterflooding may vary one from another. In this study, the focus parameter will be the water salinity and a test was done to determine the effectiveness of the DRA in different levels of salinity. To accomplish these objectives, an amount of coconut residue was processed for the extraction of carboxymethylcellulose (CMC). Then, it was used as DRA and tested by using fluid friction apparatus in different levels of salinity with 0 ppt (tap water), 10 ppt, 20 ppt, 30 ppt, 40 ppt and 50 ppt concentration. The concentration of DRA used is 400 ppm for each sample. From the test, it was found that the DRA extracted from natural waste materials (coconut residue) can reduce drag. Nonetheless, as the salinity of water increase, the percentage of drag reduction decrease. Or in other word, drag increase percentage is increased. Therefore it is concluded that, the CMC extracted from natural waste materials (coconut residue) can act as DRA to reduce drag in water injection system. However, by increasing the salinity of the water used, the capability of DRA to reduce drag will decrease. This research will make the abundance of natural waste material to turn into a resource to be utilised as DRA and hence can transform the waste to profit in terms of operation cost. This research also will contribute to the study of flow assurance as well as can determine whether the different salinity of water will affect the effectiveness of DRA

Design and engineering of microreactor and smart-scaled flow processes

This book is a reprint of the special issue that appeared in the online open access journal Processes (ISSN 2227-9717) in 2013 (available at: http://www.mdpi.com/journal/processes/special_issues/smart-scaled_flow_processes)