Effect of drag reducing polymers on the rate of mass transfer in relation to their use as corrosion inhibitors in pipelines under turbulent flow conditions

Rates of mass transfer between a turbulently flowing fluid containing CMC drag reducing polymer and the wall of a tube were measured in the mass transfer entry region using the electrochemical technique. Variables studied were polymer concentration, surface roughness and solution flow rate. Carboxymethyl cellulose (CMC) was found to reduce the mass transfer coefficient by an amount ranging from 15 to 37% depending on the operating conditions. The percentage decrease in the mass transfer coefficient becomes greater with increasing CMC concentration and Reynolds number. CMC was found to reduce the rate of mass transfer at rough surfaces (e ⁺>3) by an amount higher than that at a smooth surface. The possibility of using large polymers as drag reducers and corrosion inhibitors simultaneously in pipelines is indicated.Nomenclature I limiting current (A) - Z number of electrons involved in the reaction - F Faraday's constant - A projected (geometrical) area of the cathode (cm²) - K mass transfer coefficient (cm s^–1) - C concentration of ferricyanide ion (mole cm^–3) - e roughness height (cm) - d tube diameter (cm) - L length of transfer surface (cm) - St Stanton number (K/V) - Re Reynolds number (Vd/u) - Sc Schmidt number (v/D) - e ⁺ dimensionless height (eu ^*/v) - u ^* friction velocity [V(f/2)^1/2] (cm s^–1) - V solution velocity (cm s^–1) - f friction factor - v kinematic viscosity (cm² s^–1) - u viscosity (poise) - density (g cm^–3) - D diffusivity (cm²s^–1)     

Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions

The present study aimed to investigate the corrosion behavior of a pipeline carrying dilute pulp fiber suspensions (0.1–0.3% consistency). To examine the role played by pulp fibers on the rate of diffusion controlled corrosion of metals an accelerated test which involved the diffusion controlled dissolution of copper in acidified dichromate was used under turbulent flow conditions. Different concentrations of pulp fibers at different solution velocities were studied. The rate of mass transfer controlled corrosion of copper was found to increase by increasing solution velocity and decrease by increasing pulp consistency. The data in the presence and absence of the pulp slurry were correlated by dimensionless equations.     

Developing and fully developed turbulent flow of drag reducing fluids in an annular duct

Velocity profiles for the inner and outer flow regions of annuli are proposed for the turbulent flow of drag reducing fluids. Theoretical expressions for friction factors are developed. From the shear stress equations and the velocity profiles, estimates for the entrance lengths are given.     

Flow visualization studies of a turbulent drag reducing solution

A nondisturbing photochromic dye trace technique has been employed to study the flow profiles of water-alcohol solutions containing the drag reducing polymer Polyox at concentrations of 0.55 to 5.5 ppm. Drag reductions of from 33 to 75% were observed in a smooth glass pipe. The dye traces show a thicker wall layer for the drag reducing solutions than that for the solvent alone. The core region is relatively unaffected by the polymer at 0.55 ppm and at 5.5 ppm the relative thickness of the turbulent core region has been greatly reduced. Earlier, unpublished work of Corinthios shows effectively no core at 33 ppm. Mean velocity and apparent axial turbulence intensity profiles obtained are in general agreement with previous data in the literature obtained with other methods and in the wall region the low frequency intensity is greater than that of the pure solvent. This is consistent with the results of Spangler but not those of Seyer. Higher low frequency intensities measured in the wall region suggest that higher frequency fluctuations are suppressed and/or that the time stability of eddies is increased as indicated by the reduced frequency of wall ejections in drag reducing solutions.     

Effects of drag reducing polymers on initiation of atherosclerosis

Results from two pilot studies using White Carneau pigeons on high cholesterol diets have demonstrated substantial reduction in arterial plaque accumulations when the birds were periodically injected with dilute aqueous solutions of a drag reducing polymer (Separan AP-30) so as to maintain circulating blood concentrations of approximately 60 ppm. Initiation of arterial plaque formation may be fluid-mechanically motivated such that regions subjected to fluid turbulence, rapidly developing boundary layers, and alternate separation and reattachment, arc; the most prone lo attack. Viscoelastic fluid response, as seen in drag reducing media, is known to alter such phenomena. Comparative documentation of plaque deposition in experimental as well as control birds shows significant differences in both the aortas and coronary arteries, at optical magnifications from 20 to 15000X.     

Roles of drag reducing polymers in single- and multi-phase flows

It has become a well-known fact that finding sustainable solutions to the unavoidable high pressure losses accompanying pipeline flows to increase the pumping capacity without necessarily adding more pump stations is inevitable. Polymers, as one of the drag reducing agents which have been found to offer such an economic relieve, is the most widely investigated and most often employed in industries because they can produce drag reduction up to 80% when they are added in minute concentrations. In addition, polymer additives modify the flow configurations of multiphase flows to such an extent that stratification of individual phases is enhanced thereby making the separation of the phases at the fluid destination much easier. The achievements so far made and the challenges facing the use of polymers as drag reducers in turbulent single and multiphase flows are comprehensively reviewed. This review discusses the experimental studies of the effects of polymer additives in turbulent flows, the analytical studies, and the proposed models as well as the suggested mechanisms that explain the drag reduction. Likewise, specific areas of interest in the review include phenomena of drag reduction by polymers, factors influencing the effectiveness of the drag reducing polymers, methods of injecting the polymers into the base fluids, degradation of the polymers and industrial applications of polymers as drag reducing agents. The current and future research interests are also addressed. Although finding reveals that there are quite a lot of research in this area, most of the experimental and theoretical works are devoted to single phase flows while the remaining ones are mostly directed towards gas–liquid flows except in very recent time when investigation into the use of polymers in liquid–liquid flows is being focused. Despite this voluminous works on drag reducing polymers, there are no universally accepted models and hence the mechanisms of drag reductions by polymers.     

Electrochemical evaluation of aminotriazole corrosion inhibitor under flow conditions

The primary purpose of this study was to investigate the effect that turbulent pipe flow has on the electrochemical behaviour of a 3-amino-1,2,4-triazole (aminotriazole or 3-AT)-based corrosion inhibitor. The experiments were carried out in a 4-L laboratory pipe loop. A metallic ring made of API X52 pipeline steel was located in a linear segment of the pipe loop and acted as a test electrode. The test environment used in all experiments was a 3% NaCl solution saturated with CO₂ at 20 °C. The range of Reynolds number studied was from 6518 to 32118, assuring turbulent flow conditions in the pipe loop. Electrochemical impedance spectroscopy (EIS) was used to determine the electrochemical behavior of the steel in the environment at different flow rates and inhibitor concentrations. It was found that the electrochemical impedance of the system is dependent on both exposure time and flow conditions (Reynolds number). It was also detected that EIS data can give information on the persistence of the inhibitor film formed upon the metal surface. Therefore, in order to qualify the performance of the corrosion inhibitor, it is necessary to define the flow conditions at which it is intended to work.     

Synthesis of functional polymers under conditions of controlled atom-transfer radical polymerization

The major achievements in the field of controlled atom-transfer radical polymerization, the most promising method of living radical polymerization, are analyzed. The relationship between the structure of a regulating agent and its activity under the conditions of controlled radical polymerization, including the efficiency of metal-complex catalysts for the targeted synthesis of macromolecules with predetermined molecular-mass characteristics, chain structure, and properties, is examined. Main trends in the development of this area of polymer chemistry are highlighted.     

Inhibition and interfacial behaviour of novel amidine inhibitors against brass corrosion in 1 M HNO3 under flow conditions

Abstract

Amidine inhibitors for brass in 1?M HNO₃ were synthesized, and the electrochemical behaviours were investigated by different electrochemical techniques under flow conditions. This type of inhibitor can effectively overcome the fluid impact in flowing HNO₃ solutions for at least 24?h. The amidine inhibitors caused mainly cathodic curves to low current density and significantly strengthened the impedance under flow conditions. The relationship between concentration, flow conditions, and inhibition effects was investigated by weak electrochemical polarization curves, electrochemical impedance spectroscopy, and scanning electron microscopy. Adsorption thermodynamics indicated that all of the inhibitors function via chemisorption processes with Gibbs free energies of approximately -40?kJ/mol. A modified adsorption model was constructed based on the results of electrochemical experiments to explain why higher concentrations resulted in worsened inhibition effects due to fluid impact. The adsorption mechanism was identified by X-ray photoelectron spectroscopy, ATR-FTIR spectroscopy, and quantum chemical calculations. All of the chemistry analyses indicated that the amidine and heteroatoms contributed to surface adsorption.     

A rheological study of laminar–turbulent transition in drag reducing polymeric solutions

Presented herein are the studies of laminar–turbulent transition in micropolar and power law fluids flowing in a circular pipe. For some parametric values of micropolar and power law fluids, both depict the drag reducing properties. The parametric values of these representations have been obtained from the experimental results of Mc-Comb. It has been observed that, in both the cases, as the drag-reducing property in the solution increases, the first transition point moves towards the walls of the pipe. It is also observed that the onset of early turbulence phenomenon occurs for the drag-reducing polymeric solutions.     

Characterization of polymer adsorption in tube flow of drag reducing fluids

Elucidation of the polymer adsorption and flow characteristics at the tube wall is essential for an understanding of turbulent drag reduction. The polymer adsorbed onto the tube wall, in the flow of dilute solutions of linear random coiling macromolecules, also produces a concentrated fluid layer at the surface of the adsorption zone, as a result of the flow of the solvent micromolecules in the porous network comprising the adsorption zone.Velocity profiles are developed and used to determine the radial variation in the adsorption zone of porosity, as well as fractional surface coverages and mean separation or interpenetration distances between macromolecules in the various adsorption layers. The polymer concentration build-up in the concentrated fluid layer is also evaluated. Predictions of the latter for aqueous Polyox WSR-301 solutions are in qualitative agreement with experimental measurements and suggest that turbulent drag reduction is related to the level of polymer build-up in the concentrated fluid layer.     

Viscosity properties of suspensions at the limiting conditions for turbulent drag reduction

On the basis of a postulated mechanism of drag reduction, the overall viscosity properties of suspensions are used to establish general quantitative criteria for the upper and lower limit on the conditions at which turbulent drag reduction can occur in suspensions of rigid, elongated, nearly neutrally-buoyant particles. Experimental data obtained in drag reducing suspensions of nylon fibres in water verified, quantitatively, the criterion for the upper limit. The experimental data obtained were not sufficient for a precise test of the lower limit; however, these data did show the existence of a practical lower limit, at a value slightly larger than the predicted one.     

石油管道油品减阻剂的合成

采用本体聚合,以球形Ziegler-Natta负载型催化剂为主催化剂,三异丁基铝为助催化剂,二苯基二甲氧基硅烷为外给电子体,制备了长链α-烯烃共聚物,考察了共聚单体混合比及反应条件对共聚合的影响,并进行了放大实验,测试了共聚物的减阻性能.结果表明:在n(Al)/n(Ti)为100,n(Si)/n (Ti)为5,1-十二烯与1-辛烯质量比为1∶1,反应温度0～2℃,反应时间15天的条件下,共聚物的特性黏数和共聚单体转化率较高.制备的超高相对分子质量长链α-烯烃共聚物对石油输送具有良好的减阻效果,增输率可达20.16％.     

Conversion of yeast by hydrothermal treatment under reducing conditions

In the work reported here, baker’s yeast (Saccharomyces cerevisiae) was used as feed for the production of liquid biofuels in a continuous one-step process under hydrothermal conditions in the presence of excess hydrogen and K₂CO₃. The yeast conversion experiments were performed in an up-flow reactor under near-critical water conditions (T 330–450 °C, p 20–32 MPa). The products consisted of three phases, an oil-like organic phase, a gaseous phase, and an aqueous phase. Higher concentrations of organic carbon in the process resulted in a higher product yield. The heating value of the organic phase was up to 38.6 MJ/kg. Liquefaction of yeast without any addition of K₂CO₃ also resulted in liquid oil, but the quality and the yield of the oil product were lower. A reaction temperature of 400 °C was found to be optimal for the oil yield and quality.     

A mechanistic model of turbulent drag reduction by additives

The phenomenon of drag reduction in walled turbulent flows of polymer solutions is theoretically modeled. A new mechanistic model of a polymer molecule in a turbulent flow field is suggested. It is argued that the dominant forces on a polymer fiber in the turbulent flow field are elastic and centrifugal. According to this model, an additional route of dissipation exists, in which eddy kinetic energy is converted to polymer elastic energy by the centrifugal elongation of the rotated polymer, which in turn is viscously damped by the surroundings, when the polymer relaxes. A novel approach is then illustrated, where it is shown that this mechanistic model can be accounted for as a turbulent scale alteration, instead of addition, which enables the classical dimensional analysis of a turbulent boundary layer to apply. Using this dimensional analysis with the equivalent altered scale yields remarkable results. Correct-form velocity profiles are obtained, and Virk's asymptote and slope are predicted with no empirical constants. Drag-flow rate curves are also calculated, and compared favorably with Virk's experiments. The onset of drag reduction phenomenon is also explained by this model, and calculations of it are also compared with Virk's data. The parametric dependencies of the onset point agree well with Virk's conclusions.     

Correlation of polymerization conditions with drag reduction efficiency of poly(1-hexene) in oil pipelines

High molecular weight with long linear side branches are frequently used in oil pipelines as one of the main classes of drag reducer agents (DRAs). We studied the effects of polymerization conditions, including reaction temperature, monomer concentration and cocatalyst concentration ratio (Al/Ti), on the polymerization yield and molecular weight of the resultant poly(1-hexene) made by Ziegler–Natta catalyst and their consequent effects on the drag reduction efficiency in a loop test. The experimental results verified that the catalyst activity increased from 115 to 220 kgPH/molTi.atm, while the molecular weight of poly(1-hexene) dropped from 2100 to 1030 kDa, as the reaction temperature was increased from 0 to 50 °C. The loop test results also revealed that the highest pressure drop was achieved using the polymer synthesized at 0 °C and by subsequent increase in reaction temperature the pressure drop decreased. Furthermore, the catalyst activity increased from 143 to 262 kgPH/molTi.atm by increasing Al/Ti ratio, while the molecular weight increased up to a maximum level of 1500 kDa at Al/Ti = 143 and decreased at higher cocatalyst contents. Similarly, the results showed the maximum pressure drop of 20 % at Al/Ti = 143. Finally, by increasing monomer concentration, the catalyst activity and polymer molecular weight increased from 75 to 262 kgPH/molTi.atm for the former, and from 700 to 1800 kDa for the latter which resulted in maximum pressure drop by 25 %. Moreover, the pressure drop for each utilized poly(1-hexene) was increased proportionately with DRA’s concentration, and interestingly enough, DRAs were further effective at more turbulent flows with higher Reynolds numbers.     

Transitional behavior of polymeric hollow microsphere formation in turbulent shear flow by emulsion diffusion method

Polymeric hollow microspheres have attracted growing attention because of their unique properties and extensive applications. We report a facile emulsion diffusion process to fabricate polylactic acid (PLA) hollow microspheres driven by viscous turbulent fluid flow. The process involves the emulsification of PLA–ethyl acetate solution in the water–glycerol medium under high viscous turbulent shear flow where emulsion droplets coalesce into multiple emulsions, and the solidification of PLA by the diffusion of ethyl acetate. The addition of glycerol changed the viscosity of the continuous aqueous phase, resulting in the transition of fluid flow from inertial turbulent to viscous turbulent dominant regime and thus PLA particle size and shape from solid nanospheres to hollow microspheres. The emulsification temperature also needs to exceed the glass transition temperature of PLA to form hollow microstructure. This method allows the easy control of PLA particle shape and size for different applications.     

Wavelet autocorrelation identification of the turbulent flow multi-scales for drag reduction process in microbubbly flows

Measurement of turbulent flow was performed in a fully developed channel flow for both single-phase and microbubble injection conditions. A drag reduction was achieved by microbubble injection in the boundary layer. Further understanding of this phenomenon has a significant impact on energy saving. In this experiment, the Reynolds number was 5128 based on the half height of the channel. The particle image velocimetry (PIV) technique was used to obtain two-dimensional full-field velocity components in the streamwise direction near-wall normal plane. Wavelet autocorrelations were applied to the streamwise fluctuating velocity fields. By applying wavelet analysis, many of the shortcomings of Fourier analysis were overcome. The comparison of the wavelet analysis results between single-phase flow and microbubble flow indicated that the microbubbles drag reduction is a multi-scale mode, in which the small-scale fluctuations are suppressed.     

Characterization of drag reduction and degradation effects in the turbulent pipe flow of dilute polymer solutions

Turbulent drag reduction data were obtained at Re = 9000 in a 0.62-cm-I.D. pipe for five Polyox compounds covering a wide range of molecular weights. The concentration dependence of drag reduction was shown to obey an improved form of Virk's drag reduction equation, which was previously applied only to flows in capillary tubes. The efficiency of the drag-reducing polymer additives on a unit concentration basis at infinite dilution was determined by using a characteristic parameter, DR_m/[c], for each compound. A linear relationship was found to exist between this parameter and polymer molecular weight. The polymer degradation data were analyzed through use of a variable related to the dissipated energy in the wall region. The polymer molecular weight was found to decrease as a hyperbolic function of the dissipated energy function. By examining the change of molecular weight with respect to this function, a degradation index characteristic of the entire Polyox polymer family was established. This index may be of general application and provide a method by which the shear stability of various species of drag-reducing polymers may be meaningfully compared.     

The turbulent drag reduction by graft copolymers of guargum and polyacrylamide

Commercial guargum is known to be a shear stable drag reducing agent. However, the aqueous solutions of guargum start degrading within 8 hrs. of their preparation and after 65 hrs., they degrade completely. In the present investigation, the graft copolymers of guargum and polyacrylamide have been prepared. It has been shown that the purification and grafting enhance the drag reduction effectiveness and biodegradation resistance considerably in guargum.